Just finished the campaign, awesome game! Here are some problems I encountered (some SPOILERS!! - Steam version 1.0.18):
-Most of the merchants under the Volcano don't offer goods even though their speech hints otherwise.
-Merchant prices differ greatly. When selling items the Arcaneum merchant buys for more at 20% discount compared to the basic weapon/armor merchant at 30% discount.
-Fly prevents characters from moving after the lava chamber boss fight (normal movement works).
-If more than 3 items are put into the trading part of the merchant interface and clear all is selected afterwards the items disappear from inventory (also happens if the third item is removed by clicking on it).
-Golden Key stays in inventory after it is used.
-In Temple of Lost God, if Arwin is used to click on the tablet before the puzzle, the document does not appear in party inventory and the interactable object disappears (potentially breaking the quest).
-After the penultimate council meeting when the characters have to choose between the inn and the residence, the journal automatically advances as if the inn was chosen. When I went to the inn I encountered the scene which would have occurred if I rested there.
-Arwin has no animations after he joins the party the second time (fixed with reload, was hovering and moving without animations before reload).
-After you return from the village with Arwin (last part of the game) and enter the city, you can still control Arwin if you don't manually select your party members. I clicked on the area in front of the inn and he came running from inside. He had no follower portrait in the UI but was accepting move commands. Fixed after reload.