This Counter32 counts the number of outgoing SNMP messages dropped because their tmStateReference pointed to a cache entry that was no longer valid. Admins use it to detect internal state-tracking problems in the SSH transport model, distinct from network or authentication failures, since this reflects the device losing track of the session state needed to send a queued message. For example, a caching bug or an unexpectedly early cache-expiry timeout on the device could cause this counter to increment even when the underlying SSH session itself was healthy.