First of all, I just want to say how much I love the concept of your game, and that I had a blast playing through the EA. I remember enjoying the demo but having some skepticism on whether your team could follow through on it, but after seeing what you've gotten done so far in the EA I'm confident you can do amazing stuff if you get enough support. Will definitely back any Kickstarter for an expansion.
Okay. The bugs:
1. Elevation should affect threat radius / attacks of opportunity. I found that a character standing on a cliff edge about 15' above a medium-sized creature below them suffered an attack of opportunity when they backed away from the cliff edge.
2. Passing while you have an action left should automatically make the character Dodge. If a character has nothing else to do with their action and they are in combat there is literally no reason for them to not do it. The UI allowing the player to pass the turn with an action left is just a (small but) unnecessarily difficulty increase for players who aren't D&D veterans.
3. So, an embarrassing thing happened. My Wizard cast Sleep with themselves in the radius of effect, and put themselves to sleep. That in itself is fine (it's how the spell acts per SRD), the problem is that that crashed the game. It looks like the code that prevents incapacitated characters from taking actions also prevents them from passing their turn, which normally isn't a problem because the initiative tracker auto-skips their turn, but became a problem when I managed to get a character incapacitated on their own turn.
4. Actually, while I'm at it, maybe you could change the Sleep description to say it affects "targets" instead of "enemies". The spell behavior is correct, and as a D&D player I should have known better, but someone without D&D experience would be unreasonable in thinking, from your description, that the spell didn't have friendly fire.
5. This isn't a bug, but, the town needs more life. The amount of social encounters in the dungeons is good but I expect more, not less, of that in town. If you just added NPCs that spit one-liners like an ancient console RPG that'd still be a step up. Since you're establishing your own world you could have people reveal information about the factions and their figureheads, how the nations interact with each other... kill two birds with one stone here.
6. Sleeping creatures should be helpless and thus auto-crit by melee attacks. They're not, they're just prone.
7. Is there a reason why only one PC gets a chance to make a lore skillcheck? It's aggravating to watch a different character flub a History roll when I have a Loremaster standing right next to them. Severely limits the usefulness of what was already the least powerful subclass to begin with.
8. UI says "click to light this light" for object interactions that are not lighting lights. Or sometimes "click to open door'. Maybe you should just come up with a generic string like "click to use" and use it everywhere, that way it won't be wrong anywhere.
9. My Loremaster crafting Magic Missile scroll doesn't seem to consume resources. I could have crafted as many of the things as I had time to do so. The UI lists what resources it's supposed to consume, but, the stack size doesn't actually decrement.
10. There are a bunch of things you can't do mid-trip while travelling and it's terrible. You need to be able to turn around and go back. You need to be able to change your travel speed. You should be able to change your prepared spells when you long rest.
11. Most importantly of all (IMO), you can't cast spells while travelling. It would suck if you forgot to heal when you walked off the map of an encounter, and had to reload to fix the mistake instead of just casting the healing spells when you realized. But the real reason why this is important is because you need to cast Goodberry when you run out of food. Until you fix ration availability from merchants, Goodberry is literally the most important spell in the game....
12. Acid Arrow makes the victim lose a turn. Pretty sure it shouldn't.
13. Closing a door while the party was next to it crashed the game. The party members adjacent to the door when it closed became unresponsive. This happened inside the long rest room in the corner of the second level of Bone Keep, if it matters where.
14. The "Shield +1" found in Bone Keep actually raises AC by 4 instead of 3. Similarly the "Leather Armor +1" I found gave a base AC of 13 instead of 12.
15. Mousing over the quick item button in the combat UI should give you a tool-tip reminding you what that item is. Sometimes I would forget and when the item is a scroll you're just... well, that's some spell or another. Don't know what...
16. There really should be something in the character UI that tells you your XP or progress to the next level. People want to know this.
17. I eventually ran into Insane loot bugs late in Bone Keep. I suspect this is tied to character inventories getting too large. Dragged item from loot pile turning into different item. Not being able to drag items in loot pile - I click on them but the icon won't move. Contents of loot pile changing when I close and reopen - usually results in dozens of arrows appearing out of nowhere.
18. Bracers of Archery may be adding damage to my Ranger's shortsword attacks. I see the debug text when I hit with them regardless of what weapon I use.
19. Fighters should have Athletics as a class skill instead of Acrobatics.