You may be (probably) misunderstanding what the inside_vector does / is for.
Likely your problem arises from an incompletely closed mesh.
You should use a mesh editing took to analyze / fix your mesh and try again.
https://news.povray.org/povray.general/message/%3C5997f81e%241%40news.povray.org%3E/#%3C5997f81e%241%40news.povray.org%
3E
- BE
