I am unfortunately still getting it even with the other PR merged in :/ Reproduction:

1. switch profile. create lobby
2. swtich profile, join existing lobby
   repeat switching profile and joining with 2 or 3 players and eventually the error pops up

Hmm I'm trying those same steps and can't reproduce. Could it be that you're signing in on a clone to an account that's already in the lobby? I'm creating a new profile every time.
But, in the meantime, since this isn't game code at the moment, let's have this PR go through with the upgrade and create a ticket for that issue with repro steps.