Artifact is showing in rendered vp. Shows ok in material vp.

So, what is this? Normals are recalculated and no overlapping parts here. It looks ok in material viewport, but when I changed vp to rendered it looks like that. What can be causing this?

Another pic here in solid vp.

Get rid of the ngon (faces > 4 sides), you have at least one face with 5 sides, and make sure the face is planar

Long triangles are Nasty, try and avoid them

Check that face is also using the correct material and your UVs are ok

Sorry, maybe I should have said that I have no Ngons, no interior faces, no doubles and no non-manifold geometry. Everything is clean. The back side is completely flat. The UV maps are fine. I have even tried making new faces and reset the UV map and the problem still show up in rendered vp. Thanks for your input though.

edit: After removing and resizing some triangles, the problem was solved. I always try to avoid triangles, but to save faces I made the backside of the keyboard with some triangles on the flat areas and it worked well until I got this. Still dunno why this problem occured. And it only showed in the render vp.