Couple more to add to the pile:
Interaction between mage armor and shields is broken. Shield AC isn't added even though it should stack theoretically
No punishment for failing sleight of hand pickpocket check if in multiplayer and one player is engaged in conversation with shopkeep while other pickpockets (doesn't work in soloplay)
abusable deadzone in owlbear fight in the upper cliffs where the owlbear can neither hit you nor have enough room to jump up
while light cantrip is applied to weapon and in melee range, still getting disadvantage on attacks in owlbear encounter for "target is obscured by shadow". Might be happening elsewhere, but only place I noticed
