Very unusual ground performance despite a displayed 60+ FPS

Hi all,

I have the same problem. Not sure if since last Update, but could be. Flying low over a certain period, I have stutters from one second to the other so significantly, that MSFS is close to freezing and nearly unplayable, mostly below 1.500ft. Climbing to ~ 2.000ft, the stutters are immediately gone. Playing around with LOD or Objects makes no difference. I have nothing changed to the graphics within the last months. Deleting shader cache as recommended here made also no difference. What is strange is that it occurs after a certain period of flying low, no matter where. During regular approach in IFR, I have no problems. Any further idea what to do?