When I create my PBR material and use texture mapping it does this to the edges of my shape. Sometimes they extrude as well, in this example they are doing the opposite. Probably a simple fix as I am new to rhino. I am 73 years old.
Probably _QuadRemesh with high enough face count. Then _Weld on the resulting mesh with correct angle tolerance to get rid of mesh edges. Another way is to set a custom render mesh, extract that with _ExtractRenderMesh and do the same weld step.
On the left: box (extrusion) exploded, joined back together then set a custom mesh. On the right, extracted render mesh from the left object, welded at angle 100. Shown here is Raytraced viewport.