We have a weird issue here. Only observed in one place with one particular antenna type.
Brand new units are connected there and modem fails to register. Different modem on same antenna and SIM card registers fine. Use different antenna and FXT009 will register as well. Signal issues? I thought too, but it is not.
I tried to run AT+CCED=0,1 command and MNC (Mobile Network Code) is wrong!!! Modem tried to register against wrong provider. No wonder it fails.
Now for the weird part – any attempt to force operator or radio rescan (at+wmbs or at+cops commands) will immediately find the right operator and modem will register happily. And fault is gone. Reboot or re-power the modem and it is happy registering.
The problem is that we have few hundreds of those deployed to a customer and this particular location happens to be their test lab, so they froze the deployment until we can figure out how to fix the modem so situation like that will not happen in the field.
At this stage, I got some logs and Sierra Wireless are looking at the problem. But any help in the meantie is greatly appreciated.