Normals facing right way but some are still inverted

Hi everyone

I made a few bottles that were transparent, but when i try to make them opaque, a part of the bottle looks inverted (like on the left).

They were made in blender and other shaped bottles have the same issue, it looks like certain parts of the UV map make the polys inverted, but the normals are all facing the right way.

anyone know a way to fix this issue?