you must double-check your softphone and see if when the operator turn off the machine it is correctly sending the logout message, you might be having a development issue, i had that problem and we sent the softphone to the developers to rebuild the code in order to send the correct events in the right order.
another thing you might expect is once the operator type anything in the phone your softphone can lost the sync..that is also another problem in the code and conversation between Nortel and Genesys, remember the conversation between the hard and softphone is using your network, so you must take the logs from both sides to see what is being sended and what is being received.
Monitor an station using the testphone and make a test, then you will see if the softphone is sending the event or not.
We had a similar issues with s/w phone and hardphone being out of sync. we had to analyze the symposium logs as well to check the CTI event flow. it was resolved, after the engineers installed CTI update patches which were long pending in symposium.
you can request the switch engineer to pull the corresponding symposium logs and assist in debugging.