Well, if you are looking for anyone who may have had the same issue or know of a defect, it would help if you provided specifics on the CUCM version (exact version ID) and the firmware version of the phone model in question.
As far as removing a device pack, this is not necessary. You can simply go to the Device>Device Defaults and modify the default load ID for the 7931 phone there.
These are the paths to get to each CCX logs through CLI. They may be helpful if you are having issues accessing RTMT or downloading logs through it.
If you want to download them you have to prefix "file get " and you can add one of the options (re...