GPU usage drops at aircraft shutdown

I’m trying to debug this for weeks now.
My GPU runs at 65/75% dor the whole duration of the flight. No issue from takeoff to parking. At the exact moment I shut the engines the gpu usage drops from 60 down to 35%. There is no way to wake her up again. Does anybody have any idea? I also did a full reinstall but no luck. Maybe something is triggered in the sim after engine shut down that may cause the issue? Even if I restart the engines and take off again the usage stays at 35%