Brume 2 - Restore not working

I switched from a plastic Brume 2 to the aluminium version.

I connected the new Brume first and upgraded it to the newest Firmware. Both now have 4.2.0.

I created a Backup in LuCi in the old Brume 2 and tried to Restore from it to the new one.

When i Upload the archive in LuCi, it says: “The uploaded backup archive is not readable”

Did i something wrong?

Thank you

I have tested it and the backup file always works. Can you provide more details?