Diablo 3 patch 2.4.0 Known Issues, updated through January 19.
Achievements that are tracked with counters or multiple criteria checkboxes can visually “reset” when players enter a new game session.
Workaround: This is a visual bug only. Completeing more objectives or criteria towards the completion of the achievement will cause your actual progress to reappear for a time
Monk – Mystic Ally: Interacting with a Healing Well, dropping or equipping items, or performing other similar actions can cause players to lose health equal to the health bonus provided by the Earth Ally.
Enemies affected by Black Hole with the Event Horizon rune while the wizard has the Boyarsky’s Chip gem equipped may become stuck at 1hp and become unable to be killed
The Lianna’s Wings item model is incorrectly clipping into the player model while sheathed on the player’s back
The Custom Engineering Hellfire Amulet passive may stop functioning properly after a few minutes of play
Set Dungeon failed messages will spam players continually after failing the “Maintain Sweeping Wind” objective in the Dungeon of the Monkey King’s Garb
Not listed is the WD helm Carnevil, which has been bugged since a hotfix last week. Blizzard has been working on the problem, and today announced that a fix is in testing and should be live in the soon:
I really appreciate your patience with us while we investigate this issue. Wanted to pop in with a quick update.
We do currently have a fix in testing, and our QA team is putting it through the ringer to make sure it’s good to go (and of course, doesn’t negatively impact anything else). I don’t have an ETA for it’s arrival, but I want to confirm it is actively being worked on and we’re trying to get this hotfix to you as soon as we can.