@Piotr the first issue is a know issue that should have been fixed, but apparently isn’t in 7.30 rc (I can’t repeat it in 7.30 build of the day though)
The issue you see in V8 is of course something else that needs more investigation.
ps: I split this topic, but it should actually have been splitted in two, The first issue is I think RH-74624 Shaded display material looks like semitransparent spilled gasoline.