Melitta Barista T System error 14

Hi all
,I have a Melitta Barista T sitting on my workbench.

It has an electronics problem.
When starting everything runs smoothly.
Then when I want to pull a coffee, the machine does not grind any coffee and after a short time it says "system error 14" and the machine goes off.
I disassembled the machine and found that the grinder is driven by 4 volts from startup, but no further current flows during the grinding process itself.
Since I have read a lot about a defective Triak, I would like to try to replace it.
But which one is the one that is responsible for the grinder? The one on the heat sink, I think, is for the heating.
Am I on the right track, or am I possibly totally wrong.
Thanks for your feedback.