MK3S stops extruding filament  

MK3S stops extruding filament

Hello everyone
Months ago, I got the first issues with my MK3S. After minutes or (many) hours (it happens very irregularly), the printer stops extruding filament but continues to 'print'. Sometimes a little amount of filament still comes out by bits, sometimes nothing. After the failed print, the filament is stuck and needs to be pulled out with a reasonable amount of force.
I hoped the problem would be solved with the planned MMU-extension. Unfortunately, the problem still existed after the build was ready and I went on searching for a solution.

Changing filament was not a solution (I tried different kinds of filament and different brands).

I also bought and installed a new nozzle, hotend heaterblock and hotend heater cartridge. Finally I checked the temperature during the prints; no temperature-drop occured.

Someone familiar with this problem? Or any suggestions what I can try to solve the problem?

Hopefully, my English is understandable enough... 😉
Thanks in advance for the help.