Using 5.2 preview 2, I suddenly also noticed that reflections disappeard from objects that is under a certain size.
After testing many thing, I managed to remedy this with following command:
r.RayTracing.Culling 2 (default is 3)
Also now, to increase distance I need to use:
r.RayTracing.Culling.Radius 1000000 (default I think was something like 30000)