Found this on accident one day, thought it was hilarious, and tried to recreate it to show a friend.
It seems to only happen when I use double stolen Whirling Axes while standing still on the body. When I’m moving around he doesn’t stomp himself. It also has only happened with the Warrior NPC, but I haven’t actually tried doing double Whirling Axes on the other NPCs so maybe it’s not just the Warrior.
(sorry about the music, didn’t really plan to use the video in a bug report)