I3MK3/MMU2S printer keeps prompting filament change at end of print, with last update  

I3MK3/MMU2S printer keeps prompting filament change at end of print, with last update

For 9 months or so, my I3MK3S with the MMU2S work great!

But, after upgrading the firmware to 3.9.0-3421, I have a strange phenomenon. After each print the bed will be in the far away position, the print head in the front right position, the filament unloaded and the printer asks to press the button to insert new filament. If pressed it will load and then directly unload filament. This will happen a couple of times and then it will stop. This is very annoying because it will keep the print head heated.

My settings:

Filament sensor: ON
Spooljoin OFF
FS detection: cont

If I run the Fsensor detection check, it will ask if filament is loaded, it is not, then response: Verification failed, remove filament and try again.

Before the upgrade of the firmware it worked fine. I upgraded with Ubuntu 18.04.5.

What can I do to solve this? All help is very much appriciated.

Kind regards,

Mark