ENA 9 Brew Group problem.

How the Brew Group on ENA 9 micro is supposed to work?⏎
It stays stuck on top upper position and then motor just keeps grinding the cogs. ⏎
I followed disassembly instructions and removed and cleaned the Brew Group.⏎
A also read instructions how to disassemble the Brew Group itself. They sonud pretty complicated. ⏎
I want to understand HOW exactly the motor is stopped when Brew Group ends at top dead position. I do not see any mechanical or electrical sensors. ⏎
I also try to understand how replacing the seals can help.⏎
I can manually screw Brew Gruoup from up to down dead position. All parts seem to move. How the cycle keeps repeating?