This time around I remembered doing a screenshot.
After using Shift (Rogue) on the Abomination fight in the 58er Mono Story Quest I got stuck on sometthing that looks like map apparel (see Screenshot).
After shifting onto that I was completely unable to move or shift to another place. The enemy was still able to come up to me/hit me and after it was close enough I was also able to hit back.
Of course I could neither complete the quest nor loot the drops.
This also happenend on some other maps (3rd time for me) and it was always some kind of decorating element in the maps that made me stuck.