Solved!

After uninstalling and reinstalling SteamVR and deleting environment variables once more, which both didn't help, I found a solution.

I opened the Mixed Reality-Portal (that's the window showing up after you connect the headset).  On the l.h.s. there is a small menu bar. I choose the second icon below the three bars "Presentation of spatial limits" (or similar, it's in German on my system). Next you can choose between two modes "VR unlimited" or "VR sitting and standing". Select the latter and you will be given an option to "Center".  Do the centering and that's it.

Maybe I'll make a tips and tricks entry as I found a thread on the official forum where others ran into the same issue.

Kind regards, Michael

55 minutes ago, pmb said:

Solved!

After uninstalling and reinstalling SteamVR and deleting environment variables once more, which both didn't help, I found a solution.

I opened the Mixed Reality-Portal (that's the window showing up after you connect the headset).  On the l.h.s. there is a small menu bar. I choose the second icon below the three bars "Presentation of spatial limits" (or similar, it's in German on my system). Next you can choose between two modes "VR unlimited" or "VR sitting and standing". Select the latter and you will be given an option to "Center".  Do the centering and that's it.

Maybe I'll make a tips and tricks entry as I found a thread on the official forum where others ran into the same issue.

Kind regards, Michael

Excellent.  Very pleased you've found the problem.  And in the process, we've both learnt something that could be very useful for future tweaking ☺️

5 hours ago, pmb said:

Solved!

After uninstalling and reinstalling SteamVR and deleting environment variables once more, which both didn't help, I found a solution.

I opened the Mixed Reality-Portal (that's the window showing up after you connect the headset).  On the l.h.s. there is a small menu bar. I choose the second icon below the three bars "Presentation of spatial limits" (or similar, it's in German on my system). Next you can choose between two modes "VR unlimited" or "VR sitting and standing". Select the latter and you will be given an option to "Center".  Do the centering and that's it.

Maybe I'll make a tips and tricks entry as I found a thread on the official forum where others ran into the same issue.

Kind regards, Michael

Interesting read all of this, much appreciated but I have some doubt if this is the solution although the reset and "center" part can help.

Jfwiw, I have this problem once in a while, I then take the headset off and check if there is enough light and also that there are no lightsources (bulbs and spots) visible by the headset. In case of the latter, the headset can lose tracking because it focused on the lightsource (I assume) and when you turn your head this source becomes temporary invisible. This also counts for reflections of lightsources, mirrors and such.

 

Kind regards

4 hours ago, Gerwil said:

Jfwiw, I have this problem once in a while, I then take the headset off and check if there is enough light and also that there are no lightsources (bulbs and spots) visible by the headset.

I doubt it was lighting in my case. As soon as I switch to Windows OpenXR  the issue is gone - under the same lighting. As soon as I re-activated Steam OpenXR  it was back. Maybe reinstallation of SteamVR which I did before helped, but a test immediately after that still failed.

The issue doesn't seem to be that rare, thus more reports on potential solutions  (and causes) would be very helpful for those affected.

There is still my second issue of very poor performance under Windows OpenXR  which, however, is outside the scope of this thread. Maybe I'll put this elsewhere for discussion.

Kind regards, Michael

Old (-ish) known problem with WMR, it tends to "forget" your position (independent from the device and "seated" vs. "play area" settings BTW) likely because the orientation in your environment is kind of "adaptive", so tracking is deteriorating over time and at the end it stops working for the most part.  However, even little changes in that environment (some device with a LED, a white coffee mug at the wrong place, something covering a light source...) can make it trip faster.