strange crashes under poor receiving condition

Hardware MKR Family MKRGSM1400
1

Hi,

I have a strange effect with the MKR1400/ SARA-U201: After a couple of day's the modem crashes and something strange happen ether on the SIM or on the Network side.

This happens mostly under poor RX/TX conditions, but I think it's not necessarily bounded to them (it happens also with better condition but takes then much more time). So I guess the error occurs while the authentication process.

After the crash the only way to get a connection with the MKR and the corresponding SIM again is to:

  1. take out the SIM,
  2. put it in a different mobile,
  3. do a manual network scan,
  4. login with the different mobile,
  5. take out the SIM
  6. and put it back into the MKR.

Does anyone have a clue what this could be? I already tried to enter the network manually
with a

  1. AT+COPS=2
  2. AT+CPIN="xxxx"
  3. AT+COPS=1,2,"xxxxxx"

The last command worked at last to the point where the Operator is stored in the active profile - how ever after that, only a reset of the MKR can bring back the modem to operation - if the SIM or the Network is in the above mentioned condition. If not, everything works as expected.