The original body.stl file has a pretty weak tail, which is easy to break.
I just imported the body file into blender and thicked the weak point a bit.
To print, just use this body file instead the original and it schould work fine. (Original files: https://www.prusaprinters.org/de/prints/32814-toothless )
(The two in the photo are the original ones with the thin tail.)
The author remixed this model.