Hello.
Im having the exact same issue also using a Pico 4 Vr-Headset in standalone mode and i am 100% sure that the issue has something to do with the recent update for the imposter-avi’s.
I discovered that all users who’s fallback avatars I could see were not using the imposter function. As soon as they activated it in the options, they also were completely invisible to me, except for their name tag.
Currently, I have to manually set each user to “Shown” if I want to see their avatars, which is quite cumbersome.
Please fix this as soon as possible.
Thanks.