In Rhino, when using the bump/normal or displace slider do adjust intensity the objects turns black and then normal depending on the slider position. See image below.
It is happening with all kinds of maps and materials.
Version 2.9.0 - Preview 5
Thanks a lot. I was able to reproduce the problem at hand and our developers stated that this is actually already resolved in an internal version. So, you can expect the fix to be included with Preview 6 of course!