Cloner causing material artifacts

Hello, I imported an object that is clean / good with (3) materials. (dark cylander on left). When I Clone it, I get that weird traingle artifact that looks like bad Mat IDs, but it’s not visible on the object PRIOR to Clone.

I deleted Cloner, removed object and put back into Cloner, changed materials, etc. and nothing I do fixes it. Is this a known issue in any way?