zebra striping when set smooth

it renders this way when set solid.
and like this when set smooth.

if is showed you screenshots it would look like zebra stripes.
very annoying. i’ve deleted duplicates and ctrl+n for normals, but
it isn’t helping.

Go int edit mode and deselect all the verts and then select->non-manifold. If some verts become selected you probably have some interior faces which have to be deleted.


It found some vertices that were non-manifold but do I really have to delete them? Ain’t there anything else i can do to fix? They are pretty important.

You don’t delete the verts – you delete the interior faces. You have some faces bridging across the inside of your object.