This question already has an answer here:
- Weird line in my mirrored mesh 1 answer
So I have a screenshot for you, of the rear end of my female 3D model, and there in a strange indent going through it. Which only appears when I use a subdivision surface modifier.
And no, I am not talking about here butt crack xD I am talking about the horizontal line that goes all the way around.
It is unique from the possible duplicate due to the fact that it is a horizontal line, and thus is not a mirroring issue.