Some players are transparent from the human point of view. Perhaps most of the recently reported transparent skins are due to this bug.
Hey,
Is the issue you’re describing happening in the hub? If this is the case, this is most likely due to a feature we recently added to help combat performance issues that came with the most recent Minecraft update.
By default, we now only show you around 2/3 of players in each hub. You can use the command /toggleperformance if you wish to see everybody 
Hope this helps!