Game's a buggy as hell mess. MP with my partner has had many, many bugs. Until this patch many spells were straight up wrong in the tool tip. Unacceptable stuff, imho. Reviewers have been way too kind.

Edited to add
Played again tonight. In a fifteen minute span of playing, we had four significant bugs. First my dialogue got bugged and didn't get the speech choices (my partner did, but I was leading the conversation so that didn't matter). After a quick load that was fixed. We move to a new zone and suddenly I have a characters outlined permanently. Check settings, it's set to off. Quick load doesn't fix it, quit to menu doesn't fix it. Have to completely restart the game.

Then I listened in on one of my partner's conversations and when it was done, I was randomly stuck inside a box. Quick load later, we're going along and after climbing down a ladder my partner is teleported into a box.

Like... Honestly, I don't believe anyone who says they are playing MP bug free. This shit happens every play session for us.