I began having this problem before the 8.1 update. It only happened when I used "Here Drive". The phone would become extremely hot and then it would lose the SIM. Rebooting always fixed it. After the 8.1 update, it happened again after using "Here Drive" but now it is happening randomly, seemingly. Ah, now that I think of it, I'm leaving my GPS turned on most of the time since there are so many features of 8.1 that depend on knowing where you are but, the phone is not hot. So, perhaps the heat generated by "Here Drive" is not what is causing the SIM to un-provision.
I just removed and replaced the SIM card while the phone was on. I went to settings in order to turn off the Network and turn it back on when I saw a message telling me to restart my phone in order to take advantage of the "new features". Not sure what they are but I now know that going to network+ in "settings" is not where I wanted to go. Oh well. After restarting, my SIM provisioned, as it always does. My GPS is on, I 'll see what happens. I suspect that this is a problem with the 920. Perhaps just the RED 920. I also have a CYAN 920 and it does not overheat. Actually, my RED 920 is a replacement since my original had to be replaced due to overheating (after using "Here Drive" extensively).
If this continues, I will ask AT&T to replace my SIM, for the hell of it. Who knows, perhaps is has been baked. The circuit in the phone is "probably" built to withstand a certain amount of high temperature. If it has an OT (overtemp) protection circuit, the phone will turn off when it reaches this temperature. The SIM cards are probably not built to withstand these high temperatures. Knowing nothing about SIM cards and whether my assumptions are correct means I'm just guessing. So, if I get a new SIM card and the problem persists.... It's back to scouring the boards for possible solutions.
Trouble shooting 101.
Facebook
Twitter
Instagram