Those artifacts that appear in rendering are probably related to multiple modeling errors:
- a multitude of hidden raw geometry
- reversed faces
- missing faces, overlapping surfaces
- incorrect use of groups and layers
Normally all these modeling and working errors should be corrected and only then move to rendering.
If you still want to continue with what you have at the moment, you could render and get rid of those artifacts if you change a setting (but you will lose the texture of the section)
And in general, as MikeWayzovski has already shown you, it’s a good idea to use Mesh Clipper for rendering sections in V-ray.