Forgotten Tales

I am experiencing what I assume to be a bug during the House of Houses quest. In the basement, after talking to the first mage, I headed to the door on the upper left quadrant of the map. When I interact with the door, I get the message that my key disappears, but when I tap the green arrow to accept the message, the game leaves me on the same side of the door, and now my key is gone. I have done this 3 times now with the same result. While I don't mid the XP from repeatedly killing blinking mages to get more keys, I would also like to continue the quest. Help?

Update - apparently, the door in the upper right corner of the map is not bugged, so for the moment, it looks like I'm OK...

That door is exit only. If you go a bit farther to the right of that door there's an entrance door.