So i notice a ton of people (myself included) are running into this new bug where miraak the final dragonborn dlc boss teleports to some location in the southwest then wont come back. PLEASE bethesda notice this problem and fix asap. In my futile attempts to try and get past this bug, i have re-installed the game, reloaded saves, and tried everything i can think of. I seen videos where people kill all his dragons before fighting him as a fix to the etherial bug, but after doing that he refuses to return to the stage once hes killed.
I had this problem and others had suggested that it happened if you did too much damage and one even solved it by reverting to punching miraak to death. My character was level 40 and I usually play at higher difficulties, however I realised I had accidently left the the difficulty at adept level, so I just changed it back to legendary, the fight was harder and more time consuming and no bug happened.. It may be that if you are at lower level this bug never happens, which is why I had never seen it in previous playthroughs. Obviously they should fix it as the bug is about 4 years old now!