I tried as described several times but it didn't do the up(down)grade. What worked for me was: I had to switch off the printer, which failed (it was stuck in shutting down), so I finally pulled the power, started again with the USB stick inserted and then it automatically started to do the upgrade. So I think shutting down before updating might be the better (more failsafe) option. Finally the result is great :-) Thanks for providing the useful information and firmware here!