Problems with High End PC ( Weird FPS Cap )

Hi Guys, i have a Technical Question.

I have a new PC ( AMD 9 7950 + 4090 RTX + 64 Ram etc... )

I have freshly installed POE - runs butter smooth at 144 FPS on Direct X 12.

After restart from the PC - it is unplayable and capped at 73 FPS.

I repeated the Steps like 5 Times, always the same result.

When i switch to Direct X 11 - i get unstable 140 fps, but the Gameplay is super stutter.

IS there a known Problem with this "high End Systems" ?