Not been able to play with my friend since the "The Warden & The Paunch" DLC (modded)

GizzLow

As stated above I have not been able to play with my friend for 2 years now when it comes to a Mortal Empires COOP Campaign and we have tried everything.

Yes we usually use mods which has not been a problem in the past and this only started happening shortly after the Warden and the Paunch DLC came out, so we eventually gave up on even playing together and hoped it would resolve itself when the game is "fully" released.
Well here we are long after the last update and this **** still happens.

For protocol we did the following:
We uninstalled the game completly, and by that I mean completly including %appdata% roaming files. Any File/folder that just had the name Total War Warhammer 2 in it and the Steam Workshop folder too.

Then we looked for every mod to be compatible, started the game after installing 5 mods, closing it and so on till we had the selection of mods that we wanted.
(The game works perfectly fine in Singleplayer)

So then we even checked if the load order that we have is 1 to 1 the same which it is now and yet after all this I am still unable to join his lobby.

I hope anybody has some solutions for this problem because at this point we are basically out of options. Thanks in advance.