After logging into a dedicated server, teammates and enemy players are occasionally invisible. When it’s teammates who are invisible, they can still be located by a floating nametag and a healthbar that’s continually empty (when playing as Medic). The players are invisible only while alive; after they die, a corpse becomes visible. This state persists through multiple levels, and only seems to be affected by leaving a server and rejoining.
I’ve confirmed with other players that this isn’t just local; players are sometimes invisible to a single player, and sometimes invisible to multiple players. It seems to occur more often with people who are on my friend’s list, but that may just be my perception. I have, however, joined a server and discovered that the entire enemy team was invisible, which made for some awfully confusing combat… I thought they were just really good at hiding at first. 
I haven’t figured out any specific steps to replicate, but I’m seeing several occurrences every day so it must not be terribly uncommon.




This plus the corrupted text issue (esp. on the server browser screen) is making the game not much fun to play.