Pico 4 jittering in VR view

Using Pico Connect (/SteamVR), the game menus work OK - but as soon as I start a race the headtracking goes crazy, even just sitting still in the car there is constant jittering as I'm looking around.
Tried everything I could think of in terms of settings/restarting etc, but still, constant jittering in VR view.

(Trying Virtual Desktop (using VDXR) - the headtracking works OK, however for technical reasons Virtual Desktop is not an option for me)).

Hope there is a simple fix for this.

(Have been playing several other driving sims in VR (DR2, AMS2, PC2, RBR) for many hours without problems, so my setup should be good. Running AMD Ryzen 7 5700G, RTX 3070ti, Pico 4 wired connection)