From what I gather, many people have had trouble with the Galaxy at War mod's multiplayer system and have experienced similar "out of sync" errors too.

Essentially, when someone takes "manual control" of their units it causes this error. Thus, you cannot take direct control of any units, even when throwing grenades - otherwise someone gets booted. This is very inconvenient but I believe the dev team are working on fixing this issue. As for the files, I updated the mod which removed them because they weren't intended to be there. However, if you keep experiencing "out of sync errors" feel free to keep posting it in here. I would like more information on how this error occurs.

TL;DR
➢ Make sure you have the latest version of Men of War: Assault Squad 2.
➢ Make sure you only have Galaxy at War v0.76 and Galactic Conquest installed.
➢ Clear your localization folder or make sure the people in your lobby have the same files.
➢ Clear your resource folder of any projects you have been working on, either delete them or move them to a folder outside of the resource folder as a backup. Conflicting resource such as maps for mission making can cause the error.
➢ Do not use "direct control" in cooperative play as this is a GaW error which is currently being worked on.
➢ If you can, try LAN (last resort).
➢ If all else fails, try a fresh install of the game (last resort).

Please post your findings here!

Forum References:
➢ 1. Out of Sync Error
➢ 2. "Out of Sync Error" Discussion #2
➢ 3. GAW Discussion "Multiplayer" Desync Issues