Similar to [url]https://forum.sierrawireless.com/t/q2686-loses-registration/4750/1].
We have a bunch of modems on the field, which sample data in W32K mode and once per day send collected data via FTP to server. Many of them occasionally experience SIM failure. The modem works OK for several months, then troubles begin. We check for SIM status every hour with AT+CPIN? command, which returns SIM ERROR 13 (sometimes error 10 or even 515). CSQ level at this moment is always more than 15, typically around 20. We then perform reset via at+cfun=1. Sometimes this helps, but normally we have to repeat this procedure up to 5 times or even more. The failure can repeat itself again in few days or after several months, no pattern here.
We have similar application not using W32K and does not experience such problem. The power supply is OK (car battery). We have technician to clean SIM every month, this has no influence on modem behaviour. What always helps (for few days or months) is hard reset (power off / on). Funny, it also helps, if an SMS is waiting for modem when performing cfun=1 reset. The firmware version is 7.46 or 7.47.
So, is here some peculiarity around W32K code, I am missing or something completely different?