I think something is wrong with my setup. I’ve tried both a Thales Cinteron and a Telit FN980m and both of them have this behavior where the devices files (e.g. /dev/ttyUSB0) appear for maybe five seconds and then they disappear for about two seconds and then the pattern repeats. You can see the device coming and going in dmesg but also by just running “ls” on the device file appearance. I have the voltage set for the correct 3.3V, but it just keeps power cycling.
I can send the output of dmesg, but it pretty much just shows the device files “attached” and then a few seconds later “disconnected”.