Server Help Brother's Characters Are One By One Breaking

Me and my brother have been playing Starbound together for a long time now. Yesterday however, it stopped letting one of his characters (a new-ish Hylotl) into the server, and now today, that character still can't join,his and additionally, his endgame Floran can't join either. Both characters are getting the same error message: "Exception caught in client main-loop (EofException) Failed to read full buffer in readFull, eof reached"
We have been playing together on my universe via steam integrated multiplayer. Any help with this would be appreciated, these are both characters that have been on my server numerous times, and they just don't work now. He's pretty upset over it and I don't know what to do. Thanks for yall's time.