spartako_bot went in a minor fork and started to notify false alarm to witnesses (spartako witness producer was in the main fork and didn't missed any blocks), this is the error that I found:
2606729ms th_a fork_database.cpp:57 push_block ] Pushing block to fork database that failed to link: 0002315c15ad904d17192c8080121ba774c1a962, 143708
2606729ms th_a fork_database.cpp:58 push_block ] Head: 143799, 000231b77729fe84f473d51aabdbf31e530d1b82
2606730ms th_a application.cpp:429 handle_block ] Error when pushing block:
3080000 unlinkable_block_exception: unlinkable block
block does not link to known chain
{}
th_a fork_database.cpp:78 _push_block
{"new_block":{"previous":"0002315b615b561c0ea5eab6aa74aee790f5de0c","timestamp":"2015-10-11T00:28:30","witness":"1.6.11","transaction_merkle_root":"0000000000000000000000000000000000000000","extensions":[],"witness_signature":"1f6551667be1ad32fe674e9f4df852f0afe69450ccb396036026e97f468de4af7d1d0613c69ef2d9d35125e7a2bd7098dbc2fa1d44dff9aaa20a6a2cfa04fa5d2f","transactions":[]}}
th_a db_block.cpp:197 _push_block
Tomorrow I will change the code of spartako_bot adding a backup nodes list for prevent this type of problems.