A player starting up a module delays choosing a side during the game startup wizard; meanwhile, another Player syncs to the game and chooses a side. The first player can now select the same side.
Observed on a Vassal v3.5.5-opened game with the 2nd player using Vassal v3.5.3.
Does having one of those players resynchronize solve the issue? If not, I guess you just need to start the game over. I’m not sure it’s reasonable to expect VASSAL to be able to resolve the conflict…
Edit: This sort of thing is precisely why, in my online games, we explicitly wait for the previous person to say they’re loaded in to the game before the next person start synchronizing.
I agree it may be just something to be accepted about the way an online game starts. Perhaps, if anything, Vassal to revalidate the side choice once confirmed in the wizard could be a potential fix.
We noticed the situation before actual game start, so one player switching was the answer for us.