I can’t find the solution anywhere, which was suggested I believe by Dijker, so just for others users - in case of such fully loaded Homey, I had to re-download full firmware having Homey upside down (Recovery mode) and then I was able to perform backup for another 1-2 hour - D.
Beware of ratelimit, I think you can do 3 backups/attempt a day…
Also do not RESET Homey - just choose download full firmware.
