I probably didn’t have as much play time as many other players, only getting a handful of hours on Sunday, but I came across two dungeons that I could not complete. The primary one was one that I went into to complete a side quest where I gather three journals. I was able to collect the first two, but the third one was behind a door that I needed a key to unlock. I was supposed to kill a person to get the key, but I killed and looted everyone in the dungeon, and found no key.
The second instance where I had a dungeon key issue was in a dungeon I had to go through for the main quest line. Some time later I noticed that it wasn’t marked as completed, so I tried to go back through to do it again, but the key never reappeared. This may have been more of an issue where it was bugged in not showing as completed instead of bugged with the key not showing up.
I did not have time to try and reset the dungeons, I didn’t have enough play time, but I figured I’d still try and report what I found.