AFAICT, there are 2 issues that give those errors:

a) software issue. Reflash your device. It worked the first time. For me, it was Alarmed that gave the error, though it shouldn't and I had it installed before. However, reflash, install, all is good. Install Alarmed, it's broken and removing Alarmed didn't fix it. I tried installing each dependency and rebooting, nothing. Once the Alalrmed package was installed, the next reboot nuked GSM. No clue why. Maybe it has a bug where it nukes the alarm queue or the real time alarm. Don't know.

b) hardware issue. Had that too. Some people have a moving battery, other have a moving SIM. For me, it's a spot where, if squeezed, it resets/powers down the GSM modem. It's in the upper right corner of the battery. Squeezing the device there gets me the communication error.

Once reset, the OS tried 10 times to reconnect to the modem. If it can't, it gives me the error. I have since moved the device from back pocket to front and no issues. So long as nobody presses it, it's good.

If you want to debug further, syslogd offers nice assistance.