Dear Arturas,
I finally found the time to check the device.
Unfortunately, I can’t do a bootloader upgrade, as there are no public downloads available for u-boot firmware. I read here that Teltonika shares those only in private. Can you please do so?
I’ve also attempted to downgrade the firmware from the bootloader menu, but it seems this doesn’t accept large files - at least the connection is always reset after 6.9 MB.
I’ve now once again reset the router to defaults. No change 