Oshyan, the settings are GI cache detail 3, GI sample quality 8, supersample off (I should have tried it...
). I created a GI cache file per frame and used
20 (!!) files to blend. Rendertimes were not too bad, because I used an animated crop region with only the objects inside (about six hours for 225 frames). The background was already rendered separately.
The flickering is almost gone. The actual amount of leftover flicker can be interpreted as changing light bouncing off the ground as Doc Charley mentioned in his own thread. I'm happy with it.
The solution to render out the background with TG's native motion blur and then rendering the objects separately without MB and comping the whole thing together works like a charm.
Adding motion blur for the objects in postwork looks really good. Thus every part of the scene has it's own more or less correct blurring.
