If you are experiencing a De sync message when trying to play online with someone, try this...

Quick solution...
Go to, C:\Program Files (x86)\Steam\steamapps\common\Men of War Assault Squad 2\mods
and delete "The War Machine". Go to steam worshop page and unsubscibe and then resubcribe to the mod (mod will begin to download). Once download is finished....Reload game and re-apply mod.

If that fails...(this one is garenteed to work)
Do the above and also go to, C:\Program Files (x86)\Steam\steamapps\workshop\content
Locate "The War Machine", it will be in a folder with a number. You can open the "mod.info" files with notepad to check you have the right mod. Delete the folder containing "The War Machine".
Go back to steam workshops, un-subscribe and re-subscribe again.

This will give you a fresh install with only the latest up-to-date files.

I do not fully understand why de-syc happens with steam workshops, perhaps my frequent updates are a cause.