Ok, so this started with me having the very high resolution, and hence text on VR toolbar windows, as described in another thread here. A proposed fix was to change the PC resolution in MSFS graphics settings. I did this, and for some reason that broke VR for me. I could enter VR but after about 5-10sec the frame headset would start to shake almost like it’s loosing tracking. This reset every time I entered a different menu (for example going from main menu to settings would “fix” it for another 5-10sec before it became unstable again.) The tracking was solid in all other games so this was a bug with MSFS not a tracking issue with the headset. I tried to reset the changes I made but nothing worked. Same issue. Then disabled all mods, reinstalled Pimax software, reinstalled SteamVR and OpenXR toolkit/PimaxXR/OpenComposite. Not thing helped.
I the reinstalled MSFS from scratch, and now then I enter VR the game immediately crashes if I use SteamVR. If I use OpenXR it works (however can’t acces the OpenXR Toolkit menu for some reason…) but my frame rate is literally around 5fps in the menu or in-game. This only happens in MSFS. Tried to change MSFS settings and disable HAGS, but still same issue.
Lost at what to do now except a complete Win11 reinstall….
RTX4090, 5800x3d and 32GB DDR4. Latest Win11 updates and GeForce drivers updated.
If you are in VR view and the picture is shifting rapidly from side to side (sickening almost) then check in openXR to see if you are using NIS or FSR or CAS if NIS/FSR there is a size adjustment for the image that if set too large I noticed can cause this behavior…might check that and set it lower or try CAS and 100% sharpening. This is what I use, but I am on PIMAXXR with an 8KX…so your mileage may vary. Also this may be set too high in SteamVR as well so check that and lower it if it is.
This was not that issue, but a very prominant shaking and over sensitivity of the motion. But as this is not my issue now. Now the issue is that I only get 5-6fps, even in the menu. And I can’t access the OpenXR toolkit menu (shortcut keys does nothing) so it looks like I have an issue with MSFS and OpenXR…
And if I try and use SteamVR MSFS CTD immediately.
Is DX12 beta active? If so, go back to DX11. The last update made DX12 beta active, and I had the same issue
Tried both DX11 and DX12. Same issue.
Figured it out. Or at least got it working again. First of all I got SteamVR working again by deleting a lot of cache files by following this guide:
Then when I got SteamVR working ok, I tried OpenXR, and this time it loaded and I could use the OpenXR toolkit menu! And the fix for the 5fps problem was enabling “turbo-mode” in the OpenXR toolkit menu. Instant spike to 120fps in the menu, and my in-game fps was back to normal! 
