Yeah, post 5.0 I've noticed severe slow-down on the campaign map (even just scrolling over world event notifications). Some turns are smooth as butter and others have significant stuttering and hitching.  I play cooperative campaigns with my brother quite frequently and in our latest game (post 5.0.3) we've both been encountering desync's due to hard crashes.  These seem to be triggered when spec'ing characters after a level-up or autoresolving large battles.  There doesn't appear to be anything consistently causing the crashes (reloading the campaign and following the same sequence of events doesn't replicate the crashing 100% of the time). I'm on a 12700k/3070ti/32GB RAM and he's on a 9700k/2080/32 GB RAM. Prior to 5.0 we had no issues and despite the noticeable drop in performance after ToD dropped we hadn't had crashing prior to 5.0.3.  

I did not notice a performance drop the early turns. But past turn 100+ there is always 1 faction (usually one of the stronger ones) that stacks armies in some place and takes a really long time to end their turn. Did not happen in every campaign and the problem ends if the AI moves his armies from that place. Dark elves are usually the biggest offenders because they stack black arks trying to attack a city and they never do.

And if you try to click on your screen while the AI is doing his thing you will get the not responding pop up.