here is a piece from the log when it forked:
2015-09-28T20:08:30 p2p:message read_loop process_block_during ] received a block from peer 216.252.204.69:54183, passing it to client node.cpp:3232
2015-09-28T20:08:30 p2p:message read_loop process_block_during ] Successfully pushed block 275994 (id:0004361a7b4321512a38bc112c8c8ecd84d3e59c) node.cpp:3254
....................
2015-09-28T20:08:36 p2p:message read_loop process_block_during ] received a block from peer 114.92.254.159:62015, passing it to client node.cpp:3232
.........................
2015-09-28T20:08:36 p2p:message read_loop process_block_during ] Failed to push block 275996 (id:0004361c004527fceb33c4dfe9062a92a6421508), client rejected block sent by peer node.cpp:3346
2015-09-28T20:08:36 p2p:message read_loop process_block_during ] disconnecting client 114.92.254.159:62015 because it offered us the rejected block node.cpp:3368
...............
2015-09-28T20:08:37 p2p:message read_loop process_block_during ] received a block from peer 185.42.242.124:40060, passing it to client node.cpp:3232
2015-09-28T20:08:37 p2p:message read_loop process_block_during ] Failed to push block 275996 (id:0004361c004527fceb33c4dfe9062a92a6421508), client rejected block sent by peer node.cpp:3346
2015-09-28T20:08:37 p2p:message read_loop process_block_during ] disconnecting client 185.42.242.124:40060 because it offered us the rejected block node.cpp:3368
..............
2015-09-28T20:08:39 p2p:message read_loop process_block_during ] received a block from peer 178.62.88.151:46944, passing it to client node.cpp:3232
2015-09-28T20:08:39 p2p:message read_loop process_block_during ] Successfully pushed block 275996 (id:0004361c4c4b8410260663693fd59b7ca1977b86) node.cpp:3254
2015-09-28T20:08:39 p2p:message read_loop process_block_during ] client validated the block, advertising it to other peers node.cpp:3278
..............
2015-09-28T20:08:42 p2p:message read_loop process_block_during ] received a block from peer 178.62.88.151:46944, passing it to client node.cpp:3232
2015-09-28T20:08:42 p2p:message read_loop process_block_during ] Peer 178.62.88.151:46944 sent me a block that didn't link to our blockchain. Restarting sync mode wi th them to get the missing block. Error pushing block was: {"code":90006,"name":"unlinkable_block_exception","message":"unlinkable block","stack":[{"context":{"level" :"error","file":"application.cpp","line":417,"method":"handle_block","hostname":"","thread_name":"th_a","timestamp":"2015-09-28T20:08:42"},"format":"Error when pushin g block:\n${e}","data":{"e":"3080000 unlinkable_block_exception: unlinkable block\nblock does not link to known chain\n {}\n th_a fork_database.cpp:79 _push_bl ock\n\n {\"new_block\":{\"previous\":\"0004361c004527fceb33c4dfe9062a92a6421508\",\"timestamp\":\"2015-09-28T20:08:42\",\"witness\":\"1.6.5248\",\"transaction_merk le_root\":\"0000000000000000000000000000000000000000\",\"extensions\":[],\"witness_signature\":\"1f051e73526e48fd46a4359daaede6e5e5a8b6f451194c24caad9a1287506ef0cd026 c0ecdadb5ea35b9843dc0bd68faee59053278a7ce6e571f838a2d870bebc9\",\"transactions\":[]}}\n th_a db_block.cpp:195 _push_block"}},{"context":{"level":"warn","file":"ap plication.cpp","line":428,"method":"handle_block","hostname":"","thread_name":"th_a","timestamp":"2015-09-28T20:08:42"},"format":"","data":{"blk_msg":{"block":{"previ ous":"0004361c004527fceb33c4dfe9062a92a6421508","timestamp":"2015-09-28T20:08:42","witness":"1.6.5248","transaction_merkle_root":"000000000000000000000000000000000000 0000","extensions":[],"witness_signature":"1f051e73526e48fd46a4359daaede6e5e5a8b6f451194c24caad9a1287506ef0cd026c0ecdadb5ea35b9843dc0bd68faee59053278a7ce6e571f838a2d8 70bebc9","transactions":[]},"block_id":"0004361d1c4d414512a8ae8e99ecf2026627d08e"},"sync_mode":false}}]} node.cpp:3362
d>2015-09-28T20:08:42 p2p:message read_loop fetch_next_batch_of_ ] sync: sending a request for the next items after 0004361c4c4b8410260663693fd59b7ca1977b86 to peer 178 .62.88.151:46944, (full request is ["0004361158e0898268252af7afa90b1d59ffa354","0004361707141c5119a53184c26912df003d6ac2","0004361a7b4321512a38bc112c8c8ecd84d3e59c"," 0004361c4c4b8410260663693fd59b7ca1977b86"]) node.cpp:2354
............................
2015-09-28T20:08:42 p2p:message read_loop on_blockchain_item_i ] popping item because delegate has already seen it. peer 178.62.88.151:46944's last block the delegat e has seen is now 0004361a7b4321512a38bc112c8c8ecd84d3e59c (actual block #275994) node.cpp:2511
2015-09-28T20:08:42 p2p:message read_loop on_blockchain_item_i ] popping item because delegate has already seen it. peer 178.62.88.151:46944's last block the delegat e has seen is now 0004361bd4f6fdf618a74290b09a8a018ab7867b (actual block #275995) node.cpp:2511
2015-09-28T20:08:42 p2p:message read_loop on_blockchain_item_i ] after removing all items we have already seen, item_hashes_received.size() = 2 node.cpp:2515
2015-09-28T20:08:42 p2p:message read_loop trigger_fetch_sync_i ] Triggering fetch sync items loop now node.cpp:1083
2015-09-28T20:08:42 p2p:fetch_sync_items_loop fetch_sync_items_loo ] beginning another iteration of the sync items loop node.cpp:1022
2015-09-28T20:08:42 p2p:fetch_sync_items_loop request_sync_items_f ] requesting 2 item(s) ["0004361c004527fceb33c4dfe9062a92a6421508","0004361d1c4d414512a8ae8e99ecf20 26627d08e"] from peer 178.62.88.151:46944 node.cpp:1006
2015-09-28T20:08:42 p2p:fetch_sync_items_loop fetch_sync_items_loo ] no sync items to fetch right now, going to sleep node.cpp:1072
2015-09-28T20:08:42 p2p:message read_loop on_message ] handling message fetch_blockchain_item_ids_message_type f9797929aee8529c183c2a43787da7a9b3d24e14 size 85 from peer 23.102.65.247:1984 node.cpp:1684
2015-09-28T20:08:42 p2p:message read_loop on_fetch_blockchain_ ] sync: received a request for item ids after 0004361c4c4b8410260663693fd59b7ca1977b86 from peer 23.102 .65.247:1984 (full request: ["0004361158e0898268252af7afa90b1d59ffa354","0004361707141c5119a53184c26912df003d6ac2","0004361a7b4321512a38bc112c8c8ecd84d3e59c","0004361 c4c4b8410260663693fd59b7ca1977b86"]) node.cpp:2171
2015-09-28T20:08:42 p2p:message read_loop on_fetch_blockchain_ ] reply_message: {"total_remaining_item_count":0,"item_type":1001,"item_hashes_available":["0004361c4c4 b8410260663693fd59b7ca1977b86"]} fetch_blockchain_item_ids_message_received.blockchain_synopsis: ["0004361158e0898268252af7afa90b1d59ffa354","0004361707141c5119a53184 c26912df003d6ac2","0004361a7b4321512a38bc112c8c8ecd84d3e59c","0004361c4c4b8410260663693fd59b7ca1977b86"] node.cpp:2194
2015-09-28T20:08:42 p2p:message read_loop on_fetch_blockchain_ ] sync: peer is already in sync with us node.cpp:2213
2015-09-28T20:08:43 p2p:message read_loop on_message ] handling message fetch_blockchain_item_ids_message_type f9797929aee8529c183c2a43787da7a9b3d24e14 size 85 from peer 207.46.141.218:1344 node.cpp:1684
2015-09-28T20:08:43 p2p:message read_loop on_fetch_blockchain_ ] sync: received a request for item ids after 0004361c4c4b8410260663693fd59b7ca1977b86 from peer 207.46 .141.218:1344 (full request: ["0004361158e0898268252af7afa90b1d59ffa354","0004361707141c5119a53184c26912df003d6ac2","0004361a7b4321512a38bc112c8c8ecd84d3e59c","000436 1c4c4b8410260663693fd59b7ca1977b86"]) node.cpp:2171
2015-09-28T20:08:43 p2p:message read_loop on_fetch_blockchain_ ] reply_message: {"total_remaining_item_count":0,"item_type":1001,"item_hashes_available":["0004361c4c4 b8410260663693fd59b7ca1977b86"]} fetch_blockchain_item_ids_message_received.blockchain_synopsis: ["0004361158e0898268252af7afa90b1d59ffa354","0004361707141c5119a53184 c26912df003d6ac2","0004361a7b4321512a38bc112c8c8ecd84d3e59c","0004361c4c4b8410260663693fd59b7ca1977b86"] node.cpp:2194
2015-09-28T20:08:43 p2p:message read_loop on_fetch_blockchain_ ] sync: peer is already in sync with us node.cpp:2213
2015-09-28T20:08:43 p2p:message read_loop on_message ] handling message block_message_type 1003c4eca3a31fd0e4933c919f37b072876911dc size 133 from peer 71.19 7.2.119:1776 node.cpp:1684
2015-09-28T20:08:43 p2p:message read_loop process_block_during ] received a block from peer 71.197.2.119:1776, passing it to client node.cpp:3232
2015-09-28T20:08:43 p2p:message read_loop process_block_during ] Peer 71.197.2.119:1776 sent me a block that didn't link to our blockchain. Restarting sync mode with them to get the missing block. Error pushing block was: {"code":90006,"name":"unlinkable_block_exception","message":"unlinkable block","stack":[{"context":{"level":" error","file":"application.cpp","line":417,"method":"handle_block","hostname":"","thread_name":"th_a","timestamp":"2015-09-28T20:08:43"},"format":"Error when pushing block:\n${e}","data":{"e":"3080000 unlinkable_block_exception: unlinkable block\nblock does not link to known chain\n {}\n th_a fork_database.cpp:79 _push_bloc k\n\n {\"new_block\":{\"previous\":\"0004361c004527fceb33c4dfe9062a92a6421508\",\"timestamp\":\"2015-09-28T20:08:42\",\"witness\":\"1.6.5248\",\"transaction_merkle _root\":\"0000000000000000000000000000000000000000\",\"extensions\":[],\"witness_signature\":\"1f051e73526e48fd46a4359daaede6e5e5a8b6f451194c24caad9a1287506ef0cd026c0 ecdadb5ea35b9843dc0bd68faee59053278a7ce6e571f838a2d870bebc9\",\"transactions\":[]}}\n th_a db_block.cpp:195 _push_block"}},{"context":{"level":"warn","file":"appl ication.cpp","line":428,"method":"handle_block","hostname":"","thread_name":"th_a","timestamp":"2015-09-28T20:08:43"},"format":"","data":{"blk_msg":{"block":{"previou s":"0004361c004527fceb33c4dfe9062a92a6421508","timestamp":"2015-09-28T20:08:42","witness":"1.6.5248","transaction_merkle_root":"00000000000000000000000000000000000000 00","extensions":[],"witness_signature":"1f051e73526e48fd46a4359daaede6e5e5a8b6f451194c24caad9a1287506ef0cd026c0ecdadb5ea35b9843dc0bd68faee59053278a7ce6e571f838a2d870 bebc9","transactions":[]},"block_id":"0004361d1c4d414512a8ae8e99ecf2026627d08e"},"sync_mode":false}}]} node.cpp:3362
2015-09-28T20:08:43 p2p:message read_loop fetch_next_batch_of_ ] sync: sending a request for the next items after 0004361c4c4b8410260663693fd59b7ca1977b86 to peer 71. 197.2.119:1776, (full request is ["0004361158e0898268252af7afa90b1d59ffa354","0004361707141c5119a53184c26912df003d6ac2","0004361a7b4321512a38bc112c8c8ecd84d3e59c","00 04361c4c4b8410260663693fd59b7ca1977b86"]) node.cpp:2354
..............
2015-09-28T20:08:43 p2p:send_sync_block_to_node_delegate send_sync_block_to_n ] Successfully pushed sync block 275996 (id:0004361c004527fceb33c4dfe9062a92a6421508) node.cpp:2935
..............
2015-09-28T20:08:43 p2p:send_sync_block_to_node_delegate fetch_next_batch_of_ ] sync: sending a request for the next items after 0004361c4c4b8410260663693fd59b7ca1977 b86 to peer 71.197.2.119:61371, (full request is ["0004361158e0898268252af7afa90b1d59ffa354","0004361707141c5119a53184c26912df003d6ac2","0004361a7b4321512a38bc112c8c8 ecd84d3e59c","0004361c4c4b8410260663693fd59b7ca1977b86"]) node.cpp:2354
...............
2015-09-28T20:08:43 p2p:message read_loop on_blockchain_item_i ] popping item because delegate has already seen it. peer 109.73.172.144:43494's last block the delega te has seen is now 0004361a7b4321512a38bc112c8c8ecd84d3e59c (actual block #275994) node.cpp:2511
2015-09-28T20:08:43 p2p:message read_loop on_blockchain_item_i ] popping item because delegate has already seen it. peer 109.73.172.144:43494's last block the delega te has seen is now 0004361bd4f6fdf618a74290b09a8a018ab7867b (actual block #275995) node.cpp:2511
2015-09-28T20:08:43 p2p:message read_loop on_blockchain_item_i ] popping item because delegate has already seen it. peer 109.73.172.144:43494's last block the delega te has seen is now 0004361c004527fceb33c4dfe9062a92a6421508 (actual block #275996) node.cpp:2511
...................
2015-09-28T20:08:43 p2p:message read_loop on_blockchain_item_i ] popping item because delegate has already seen it. peer 188.138.122.20:60328's last block the delega te has seen is now 0004361a7b4321512a38bc112c8c8ecd84d3e59c (actual block #275994) node.cpp:2511
2015-09-28T20:08:43 p2p:message read_loop on_blockchain_item_i ] popping item because delegate has already seen it. peer 188.165.233.53:1776's last block the delegat e has seen is now 0004361a7b4321512a38bc112c8c8ecd84d3e59c (actual block #275994) node.cpp:2511
2015-09-28T20:08:43 p2p:message read_loop on_blockchain_item_i ] popping item because delegate has already seen it. peer 188.138.122.20:60328's last block the delega te has seen is now 0004361bd4f6fdf618a74290b09a8a018ab7867b (actual block #275995) node.cpp:2511
2015-09-28T20:08:43 p2p:message read_loop on_blockchain_item_i ] popping item because delegate has already seen it. peer 188.165.233.53:1776's last block the delegat e has seen is now 0004361bd4f6fdf618a74290b09a8a018ab7867b (actual block #275995) node.cpp:2511
2015-09-28T20:08:43 p2p:message read_loop on_blockchain_item_i ] popping item because delegate has already seen it. peer 188.138.122.20:60328's last block the delega te has seen is now 0004361c004527fceb33c4dfe9062a92a6421508 (actual block #275996) node.cpp:2511
2015-09-28T20:08:43 p2p:message read_loop on_blockchain_item_i ] after removing all items we have already seen, item_hashes_received.size() = 1 node.cpp:2515
2015-09-28T20:08:43 p2p:message read_loop trigger_fetch_sync_i ] Triggering fetch sync items loop now node.cpp:1083
2015-09-28T20:08:43 p2p:fetch_sync_items_loop fetch_sync_items_loo ] beginning another iteration of the sync items loop node.cpp:1022
2015-09-28T20:08:43 p2p:fetch_sync_items_loop fetch_sync_items_loo ] no sync items to fetch right now, going to sleep node.cpp:1072
2015-09-28T20:08:43 p2p:message read_loop on_blockchain_item_i ] popping item because delegate has already seen it. peer 188.165.233.53:1776's last block the delegat e has seen is now 0004361c004527fceb33c4dfe9062a92a6421508 (actual block #275996) node.cpp:2511
.......................
2015-09-28T20:08:43 p2p:fetch_sync_items_loop fetch_sync_items_loo ] beginning another iteration of the sync items loop node.cpp:1022
2015-09-28T20:08:43 p2p:fetch_sync_items_loop fetch_sync_items_loo ] no sync items to fetch right now, going to sleep node.cpp:1072
f>2015-09-28T20:08:43 p2p:send_sync_block_to_node_delegate send_sync_block_to_n ] Failed to push sync block 275997 (id:0004361d1c4d414512a8ae8e99ecf2026627d08e): client rejected sync block sent by peer: {"code":10,"name":"assert_exception","message":"Assert Exception","stack":[{"context":{"level":"error","file":"vesting_balance_eval uator.cpp","line":103,"method":"do_evaluate","hostname":"","thread_name":"th_a","timestamp":"2015-09-28T20:08:43"},"format":"vbo.is_withdraw_allowed( now, op.amount ) : ","data":{"now":"2015-09-28T20:08:33","op":{"fee":{"amount":50000,"asset_id":"1.3.0"},"vesting_balance":"1.13.30","owner":"1.2.22404","amount":{"amount":"6400000000 ","asset_id":"1.3.0"}},"vbo":{"id":"1.13.30","owner":"1.2.22404","balance":{"amount":"6392481409","asset_id":"1.3.0"},"policy":[1,{"vesting_seconds":86400,"start_clai m":"1970-01-01T00:00:00","coin_seconds_earned":"552223993737600","coin_seconds_earned_last_update":"2015-09-28T20:07:51"}]}}},{"context":{"level":"warn","file":"vesti ng_balance_evaluator.cpp","line":109,"method":"do_evaluate","hostname":"","thread_name":"th_a","timestamp":"2015-09-28T20:08:43"},"format":"","data":{"op":{"fee":{"am ount":50000,"asset_id":"1.3.0"},"vesting_balance":"1.13.30","owner":"1.2.22404","amount":{"amount":"6400000000","asset_id":"1.3.0"}}}},{"context":{"level":"warn","fil e":"evaluator.cpp","line":42,"method":"start_evaluate","hostname":"","thread_name":"th_a","timestamp":"2015-09-28T20:08:43"},"format":"","data":{}},{"context":{"level ":"warn","file":"db_block.cpp","line":609,"method":"apply_operation","hostname":"","thread_name":"th_a","timestamp":"2015-09-28T20:08:43"},"format":"","data":{}},{"co ntext":{"level":"warn","file":"db_block.cpp","line":592,"method":"_apply_transaction","hostname":"","thread_name":"th_a","timestamp":"2015-09-28T20:08:43"},"format":" ","data":{"trx":{"ref_block_num":13848,"ref_block_prefix":996090894,"expiration":"2015-09-28T20:08:54","operations":[[33,{"fee":{"amount":50000,"asset_id":"1.3.0"},"v esting_balance":"1.13.30","owner":"1.2.22404","amount":{"amount":"6400000000","asset_id":"1.3.0"}}]],"extensions":[],"signatures":["202c842047ea693db88068f8a5cb2e289d 372a8ab1226655695e7db2a2a427c7d41ff6887c12e5769aebc2e4e70953c17b95fd423b44ac03696cd413fd67c55aef"]}}},{"context":{"level":"warn","file":"db_block.cpp","line":495,"met hod":"_apply_block","hostname":"","thread_name":"th_a","timestamp":"2015-09-28T20:08:43"},"format":"","data":{"next_block.block_num()":275996}},{"context":{"level":"w arn","file":"db_block.cpp","line":195,"method":"_push_block","hostname":"","thread_name":"th_a","timestamp":"2015-09-28T20:08:43"},"format":"","data":{"new_block":{"p revious":"0004361c004527fceb33c4dfe9062a92a6421508","timestamp":"2015-09-28T20:08:42","witness":"1.6.5248","transaction_merkle_root":"00000000000000000000000000000000 00000000","extensions":[],"witness_signature":"1f051e73526e48fd46a4359daaede6e5e5a8b6f451194c24caad9a1287506ef0cd026c0ecdadb5ea35b9843dc0bd68faee59053278a7ce6e571f838 a2d870bebc9","transactions":[]}}},{"context":{"level":"warn","file":"application.cpp","line":428,"method":"handle_block","hostname":"","thread_name":"th_a","timestamp ":"2015-09-28T20:08:43"},"format":"","data":{"blk_msg":{"block":{"previous":"0004361c004527fceb33c4dfe9062a92a6421508","timestamp":"2015-09-28T20:08:42","witness":"1. 6.5248","transaction_merkle_root":"0000000000000000000000000000000000000000","extensions":[],"witness_signature":"1f051e73526e48fd46a4359daaede6e5e5a8b6f451194c24caad 9a1287506ef0cd026c0ecdadb5ea35b9843dc0bd68faee59053278a7ce6e571f838a2d870bebc9","transactions":[]},"block_id":"0004361d1c4d414512a8ae8e99ecf2026627d08e"},"sync_mode": true}}]} node.cpp:2959
2015-09-28T20:08:43 p2p:send_sync_block_to_node_delegate send_sync_block_to_n ] disconnecting client 104.155.223.175:32832 because it offered us the rejected block node.cpp:3073
....................
2015-09-28T20:08:56 p2p:send_sync_block_to_node_delegate send_sync_block_to_n ] Successfully pushed sync block 275997 (id:0004361d7bf5aecfd85eac9e45b1d1e84287a640) node.cpp:2935
...................
2015-09-28T20:09:09 p2p:message read_loop process_block_during ] Successfully pushed block 275998 (id:0004361e9fceb5c9825c54df7adb585bc4976602) node.cpp:3254
....................
2015-09-28T20:09:15 p2p:message read_loop process_block_during ] Successfully pushed block 275999 (id:0004361f189606417518259ba750f34aff126187) node.cpp:3254
.....................
.................
...............
b>2015-09-28T20:26:24 p2p:message read_loop process_block_during ] Successfully pushed block 276099 (id:000436831df20b58af1fda3d1439dd6c1423ec24) node.cpp:3254
...............
forked at block 275997.
from the log, it have received the correct block 275997:0004361d1c4d414512a8ae8e99ecf2026627d08e
but it denied it.
then switch to the wrong block: 0004361d7bf5aecfd85eac9e45b1d1e84287a640