I may have found the culprit, thank you! Sadly I cannot test on WinMR myself (loaned out my Odyssey), if you could test the build I put here:
https://www.dropbox.com/s/rg7brbvy99tk6hs/APOTU_Steam_v0.75b3.zip?dl=0
... and let me know, would be very helpful! I'll ask on twitter as well.

Thanks!

naam

Alright, I think I fixed it! Works on my side with an Odyssey, seems my Unity version had a nasty WindowsMR bug, I upgraded the project. Hope you can still have fun with it!