bitcrab have you tried
update_asset TCNY null {  "id": "1.3.734",  "symbol": "TCNY",  "precision": 4,  "issuer": "1.2.121",  "options": {    "max_supply": "1000000000000000",    "market_fee_percent": 0,    "max_market_fee": "1000000000000000",    "issuer_permissions": 511,    "flags": 128,    "core_exchange_rate": {      "base": {        "amount": 103,        "asset_id": "1.3.734"      },      "quote": {        "amount": 46825,        "asset_id": "1.3.0"      }    },    "whitelist_authorities": [],    "blacklist_authorities": [],    "whitelist_markets": [],    "blacklist_markets": [],    "description": "smartcoin defined by transwiser",    "extensions": []  } true
 
That should set your permissions and your flags back to where they were.