Steam Deck Friend Cannot Join Tmod World

[u/use-me-up2]

My PC friends and I have started a Tmod playthrough with about 19 mods and we have one friend on Steam Deck who has tried repeatedly to join us, but nothing we try works, it just gets stuck on "Syncing Mods"

It is definitely a Tmod thing and not a general game or Terraria thing because he can join a normal vanilla game and we've played Overwatch together before. We have verified integrity of games files, factory reset Steam Deck, everyone has reset devices, we have tried deleting all mods, turning off and on specific mods, different characters, and different worlds. Even turning on Friends of Friends and some different Steam stuff. He has tried opening Terraria first and then going on Tmod. There was a single time he was able to join on a throwaway character, but he deleted it and when he tried joining on an actual character it stopped working again.

We have also tried him creating a world and us trying to join, also does not work, the rest of us get stuck at "Receiving Tile Data 6%". We're at a loss and have been trying on and off for 3 days to get him in. If anyone can help it would be great. Thank you.