I have RUTXR1 with Firmware RUTX_R_00.07.11.3
The system prompts and recommends, Modem Firmware update
Current modem firmware EG06ELAR04A07M4G
Same error when attempting update from GUI and SSH
Noted this is a recurring theme across other models sharing this modem, and on firmware releases of it prior to 08.
I also concur with the earlier remarks from others about the auto-closure of topics which limits your ability to identify recurring issues, of which this one is years old.