Anyone else having periodic severe stutters post SU12, despite major CPU/GPU/VRAM headroom?

To me it seems it is happening only on the second flight of a simulator session.
Since the logbook doesn’t work at all when you simply continue a flight, I always return to the main menue.
Then I prepare the next flight including loading a flightplan from simbrief and setting my departure position to the gate/spot I had parked in the previous flight.
That second flight can be slightly jittery to totally unusable. No real pattern when one or the other happens.

Mostly I only have time for one flight so it is no big deal for me as such, but it is annoying since I did not have this until SU12.