We are maybe 30ish hours + into our save on the preview branch, and things have basically hit a brick wall. The host (me) everything seems normal but combat is 100% unplayable for any co-op partners. Enemies stand in place, rubber band, and do damage to you while 30 meters away.
We've taken two cities and basically have given up on the save, it's literally unplayable for any of the non-host players outside of just standing at a crafting bench or building a house.
Nothing on my CPU is over ~40% usage, even in combat, and running with a smooth 100+ fps. Network is out of the question, we all live within a mile of eachother (and have fiber).