This is the second time I've this bug, and I don't find any solutions to solve it :
I've strange triangles appear on modelisation like attached file.
It's a simple scene with only plane and two lights..
I've try lots of things, new modelisation did same problem..
DirectLighting / PathTracing / PMC did same problem.
I already try merging in new scene, same problem.
I f anyone have an idea

Thanks