Its not texture related at all if theres no texture. Its not uvs either.

The base mesh is clearly quads looking at it from here.

Okay that subd on the right, that looks like you have added level edits around those areas. You can do two things:

firstly: check in the hypergraph for blind data nodes, if they are there, then select those and delete them, your mesh may drop its shader when you do it but dont worry just re-apply it.

secondly: with the base mesh (not subd) simply export it as an obj. that will get rid of any 'junk' on the mesh. Then re-import the mesh and turn it into a subd again, or just to text hit smooth preview (keyboard 3) and do a test render

cheers
J