Ubisoft recently released a patch for Assassin's Creed Valhalla, addressing a lengthy list of issues. However, according to one particularly popular Reddit thread (and personal experience), it also introduced a new bug that randomly inhibits character speaking animations. Instead of forming words, character faces exhibit a blank stare during conversations.
From what I can tell, there isn't any rhyme or reason to the bug -- it just filters in and out at times. It doesn't ruin the experience in my opinion (you can still hear the audio), but it's a little distracting.
Valhalla is a massive game, so a few bugs are expected. The biggest issue to me (which I still experience) is when Valhalla inexplicably stops auto-saving progress. I've spent a healthy 80 hours exploring Norway, England, and the realm of Asgard -- but I've lost about 10 of those hours due to this save bug. There's something soul-crushing about redoing missions and such.
I misjudged Valhalla at first and now thoroughly enjoy it, but such a crippling bug isn't acceptable.
Fingers crossed that these issues are fixed soon.