Thanks, that looks all as expected. I cannot explain right now, why this wouldn't work on this setup - the multibounce reflections should kick in, once the camera stops moving ("restmode") or when you do an image capturing.
hi Clemens,
I updated my nvidia drivers without success.
But, for some reason, new scene render pretty "correct" with reflections (see below)
Maybe some old settings was still stored in my old scene and even I resaved it those have still remain
Fun Fact: in my old scene when I switch from Ultra to High, instantly the mirrors reflect correctly, but in restmode they appear white.