Is this for any combat, or just if there are a lot of opponents, or something?
Yes, any combat, almost always.
Does saving and reloading help?
Haven't tried that but don't think it will help since it happens every time I start the game, not after a while of playing.
Does this happen if the host tries the same fights in single player?
Seems that only happens with coop. Playing coop over lan atm. Joining the game from the lobby.
We did joined using the GOG invite before but I rather join using local network than going thru the online gog server?. I don't know should I try joining with GOG instead of direct local would that make a difference?