Some of these are probably already known or given by others. These are the issues that I recall encountering during my playthrough. Spoilers ahead.
UI:
1. When picking up items from the ground individually, if I my inventory had a lot of items, it would grab items from the inventory instead. In order to interact with the ground items I would have to scroll the inventory to the bottom.
2. At one point, I'm not sure when, the equipped main/off hand section for all the characters disappeared and I was completely unable to change out my weapons/shields/torches etc. Restarting the game fixed the issue.
Gameplay:
1. If entering in to a surprise conversation while in stealth and exiting in to combat you are still in stealth and able to initiate a surprise round. This happened for me at both the vampires and the wizard at the end of the tower. While I appreciated the free round and it may have saved my ass, specially with the vamps, I don't think they should have been surprised by me after having just had a chat.
2. It seems that getting surprised while resting is very common. In my playthrough out of about 8 random encounters in only 1 was I not surprised regardless of my fatigue level. I understand that's a very small sample and maybe I was just unlucky. I only add this because I saw another person making similar comments.
3. World map fatigue bar does not reset/reduce from sleeping outside of main map travel.
4. Not sure if bug of just not implemented. Flanking does not grant advantage.
5. Darkness and disadvantage. Partially lit and unlit seem to be extremely common effects. It also seemed to impact me more than the enemy. I would see my rolls going through with disadvantage and theirs would go through normally a lot, and no my characters were not holding torches or candles. My characters' dark vision seemed to have no effect on this status regardless of distance.
6. Enemy loot would sometimes over generate, specially from skeleton archers it seemed. They would drop multiple loot bags containing dozens, if not hundreds, of arrows. Occasionally they would drop extra ration packs as well. Zombies also for some reason seem to love dropping 1 arrow upon death.
7. Unable to interact/converse with Annie properly to figure out the story behind the mystery man in the tavern. First time I talked to her she told me not to ask her about it. Quest still says to talk to her but there is no conversation options to continue the quest line.
MISC:
1. Guardian Spirits spell is missing its icon image.
2. Several spelling/grammar issues in text. Only one comes to mind right now, "squeletons".
3. Scroll of Lightning Bolt is called Scroll of Fireball, didn't actually test to see if this impacted functionality.
I'm sure there were some other things that I'm just not remembering right now but those are all the ones that really stuck out to me.