Saved game in Windows forgetting sides when loaded in linux

Has anyone else noted this behavior?

Friend and I have been playing Totaler Krieg module online for a few months. Both of us were running windows. I switched to Linux Mint a few weeks ago and everything appears to be working correctly but today was our first session after i switched. After connecting online this morning (I loaded the saved game on my system and everything appeared correctly on his screen as normal), my opponent noted strange behavior. All of his hidden information (card hands, pending cards, etc.) was hidden from him, and all of my hidden info was visible to him. It looked like we were both in the game on the same side.

I have the only save game file. When we connect using windows machines, I am placed on the correct side and, after my opponent joins the game the saved information is sent to his machine and he is correctly placed on the opposite side and can only see his own hidden info, not mine. When I load the module and our saved game on my linux machine everything looks correct on my screen, but when my opponent joins the game from his windows machine, he sees my information, not his own.

We tried it a couple of times with the same behavior. My next step is to create a windows VM

VASSAL 3.2.17
Module:Totaler Krieg! (2nd Edition) / Dai Senso 10.65
Me: initially Windows 10pro 64 now Linux Mint 19.2 (4.15.0-62)
Opponent: Windows 10 home (32 i think)

Quick guess: You setup your Linux machines with a different username and/or password than your Windows machines.

Almost certainly correct, but note that it is only the module password that matters. Different usernames work fine.

The behavior they describe suggests a password problem, but it does not match what I would expect to see if the Linux guy used a different unique password. The fact that both players see the same thing suggests that in the Linux setup, they are now both using the same password. Perhaps both players ignored setting up their passwords, and now they are getting side effects for null passwords?