For the Fox Ears, Im having trouble pinpointing where it might come from exactly, but it seems to be partly due to adding the quality prompt: "nice ears". It seems that when the prompt contains the word "ears" (and not "ear" somehow) that the AI generates some kind of Fox Ears (or sometimes bunny ears - but rarely)
As for the error, I started a new playthrough to test it and it appears to be found on the first floor too. The ennemies that do it are the Satyr, Reptilian and Redjaw Hunter (that I encountered). The bug didn't happen for the False Werewolve and Hellhound. This only happened with a custom Warrior Character??? Tried it with a ranger and it didn't happen.