Reflections and double faces

I am using ray mirror on stainless steel and I am sometimes getting distortions in the reflections. I think this is because of double faces in the same plane. These distortions seem to be reflected to other objects. Has anyone else had this problem? Would faces close to the same plane cause problems? How could I purge extra faces easily?

In Edit mode, W, Remove Doubles.

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That works but it comes from an Autocad dxf so some faces don’t purge. I think 3ds will do it.

After removing doubles you could go Ctrl-Shft-Alt-M in Edit mode with all verts unselected to find non-manifold geometry. It’ll highlight offending geometry and you can delete Faces (don’t delete verts. if you have loose verts after deleting faces you can use P (seperate), All Loose Parts).

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That worked. And Face Select to grab them.