1. Discontinuous endorsement: the endorsement of a commercial acceptance bill is discontinuous and the signature is invalid.

2. Inconsistent seal: If the seal on the commercial acceptance bill is inconsistent with the seal kept by the bank, the bank will refuse to accept it, resulting in the failure of signature.

3. Inconsistent acceptance date: If the acceptance date of a commercial acceptance bill is inconsistent with the actual collection date, the bank will refuse to accept it, resulting in the failure of signature.

4. Inconsistent endorser information: If the actual payee information on the commercial acceptance bill is inconsistent with the endorser information, the bank will refuse to accept it, resulting in the failure of signature.

5. The bill has nothing to do with the endorser: the commercial acceptance bill has nothing to do with the endorser, and the bank will refuse to accept it, resulting in the invalidation of the signature.