Sometimes the errors 'SendData Invalid To argument' followed by 'ProxySendDataMulti' error can occur in pairs in the CSPNT event log.
These errors are very likely not real problems.
This error occurs when a message is received from the host, while that specific device where its meant for is not online (client is not online).
This can typically happen with printer sessions, because for a printer the host might sometimes sent test print messages to the client, even when the client has not requested for it. If at that moment the client is not online this error is occurring.
Please note this error is reported as two errors:
-The Netbios DL reports : 'SendData Invalid 'To' argument' because the To destination is not available (not online).
-This then leads to an error in the UL object reporting the 'ProxySendDataMulti....' error.