At the moment I'm trying to render another animation very similar to my "...and yet another sci fi scene..." scene, which was rendered with the path tracer as well.
I adjusted some shaders, moved the objects a bit, and animated the camera differently. There is no atmosphere involved, and the lighting I used is not much different from my previous scene.
In my first tests of the actual animation I encountered some really heavy flickering. There was no flicker at all in the other one. I created a GI cache file, but the flickering was still there. This is really weird.
So here is my question: are there any other reasons for GI flicker using the path tracer? I know, that if clouds are in the scene it might be a problem, but there's nothing.