This counter increments when an accounting response's authenticator or signature fails validation, again almost always indicating a shared-secret mismatch, but caught on the accounting exchange specifically. Because accounting messages are typically sent after a command has already been authorized and executed, a rising count here means the switch is executing commands successfully but silently failing to log them, a dangerous blind spot for anyone relying on TACACS+ accounting for compliance. For example, an environment that changed its shared secret but only updated the accounting server's key would see this counter spike while logins and command execution keep working normally.