Here's an interesting one, running on Warband 1.143, Steam version, with a fresh Brytenwalda 1.38 install and 1.38 save game.
I loaded the game in WSE to set up a multiplayer battle, which worked just fine. Had the game set up, then had Warband crash on me. Tried to set the game up again, but the multiplayer option from the main menu defaulted to the standard multiplayer modes (as expected). Then I loaded the save game to start the battle again, and that's where the weirdness begins.
The options "Set up multiplayer battle" and "Give me time to save" were gone. Tried re-loading this and a couple different save games, but I never got those options back. When returning to the main menu and loading multiplayer again, I got the option to host Co-op siege and Co-op field battles that weren't there before as game modes, but would actually crash the game when selected.
Then I decided to load the game without WSE, and lo and behold, getting into the fights I was presented with a "use multiplayer battle result" option, despite me never actually fighting that battle. So apprently, it logged me as always having retreated, and if I do select to use the MP battle results, it keeps cycling, always displaying the same casualty report, but never actually affecting the battle, and it always comes up with "You have X troops against the enemy's Y troops remaining" with X and Y being constant the entire time. It happens with every battle in every save game in Brytenwalda. The MP battle results, after careful observation, are also always the same ones used.
I've tried Battle Time by itself in native Warband, which had no such problems, which leads me to think that Brytenwalda is having issues processing a cached battle result, though I've never had it occur to me before that the options to start a multiplayer battle just vanished.