Before you go jumping to a new revision, put a user in debug mode. Then after it happens to that user, check the logs.
After that, if it isn't clear what is happening from the logs, I would open a TAC support case. They can help you determine if upgrading will solve this problem.
Basic Troubleshooting
1. Put your device in debug logging on the controller: conf t, logging level debugging user-debug your-device-mac
2. Simulate the failure
3. Now look at the logs: show log user-debug all | include your-mac-address
TAC will ask for this anyways. So it's a good place to start.
Zach