Why do you always suggest flashing the firmware from r051? Where I can see this firmware? Do you have experience with flashing this firmware? What does it do?
You don't seem to understand that we have two devices and two different firmware. Flashing the router with a new firmware will not help the lte modem firmware in any way. And by flashing r051, there is a high probability of finally breaking everything.
_ameee broke lte modem, obviously executing different commands, not quite understanding what he was doing. How to restore it is not clear, you need a full firmware for the lte modem from r281, then there is a chance to flash it and restore work. The second option, as suggested by
L E N A R, is to try to recover data such as IMEI, SN, etc. on the router via ubus call. All this data can be viewed on the router itself or through fw_printenv