My 925 was rock solid until 8.1 DP. At first it started freezing occasionally, mostly at night while charging. The freeze ups continued to increase until I was soft resetting the phone every morning and a few times a day. That's when I decided it was time for a hard-reset. At first that seemed to solve the problem - it went for about three days without a freeze up. But then it happened, and then again, and eventually it was back to freezing every night.
My next plan was to start uninstalling apps, one each day to see if I could identify the culprit. Since the problem seemed to mostly occur at night while charging, I though I would start with the Battery app. But that got me thinking - what was different about the phone settings at night. For one, the phone was in Quite Mode. Also, the glance screen turned green. Then it hit me, the Glance screen! I always knew the exact time the phone froze because the glance screen showed the time. And occasionally, the numbers would only be half displayed (clipped) - so the problem occurred while the screen was updating. Plus, the glance screen was set to always stay on while charging which explained why it didn't happen as often during the day (I have a charging stand at work also).
So - I changed the Glance setting to not stay on while charging and poof - no more phone freezing!
My guess is the problem has something to do with the video memory. Hopefully the Nokia Cyan firmware update will fix this, but knowing AT&T, it could be months before they release Cyan.
[Update]: The phone still occasionally freezes.