After failing a Nightmare Dungeon, Reddit user u/OnePunchGus noticed that their character began behaving strangely.
r/Diablo Post on Nightmare Dungeon Bug
Posted by u/OnePunchGus on r/Diablo
While this bug has been around since launch, it still appears that characters will continuously fall to the ground after a player has failed a Nightmare Dungeon. Commenters in the thread joked that this happened because the character was either too tired or pouting because of their recent failure.