Hello,
Note with this one.
Kindly try executing the command below in the CLI of the router.
gsmctl -A 'AT+QCFG="ltesms/format",1'
After executing the command, do a ‘logread -f’ and do a testing again and see if it will fixed your issue.
Note that this information is base on this query which is having the same issue.
Let me know the results.
Best regards,
Rob.