If it happens it´s also not possible for that "stuck" player to join from an other console, instead of useing Spilt screen
It also happens when one Player is in the 2nd or 3rd person camera in the beta-version 1.18.0.27
It can also happen when you don't wear any amour
Steps to Reproduce
1. Open an World
2. Use an 2nd controller to join (press menu) on the world (with another account)
3. Press menu und open the profile
4. Now you can't see your achievements and your own skins
Here is also an video, maybe it helps
[media][media]
I hosted an Server on my Raspberry Pi4, on PC i was able to join, on the xbox wasn't possible
Version 1.20.32