I’m having this same Portal 2 headtracking issue; doesn’t happen in Half-Life, or HL: Episode 1 (not sure about Episode 2); whenever I move my head, a subtle swimmy rotation echoes for a moment, then stops.
vorpX scanning & settings have no effect…the behavior remains unchanged.
(This was my first ever Portal 2 session with vorpX, yesterday, 2020-05-20; it directly followed a vorpX update).
Edit:
VorpX version 21.2.0.3