I had to drop back to 18.5.1/18.6.1 because of issues with 18.7.1 in RFactor 2. About every 15 minutes, the VR headset (Lenovo) running the latest Steam beta build and reprojection set to either auto or motionvector on Windows10 will just go black for about 3 seconds. It then returns to normal. Of course, in sim racing that means you're snuggled up to a wall and it kind of breaks the game. Both 18.5.1, which it now seems to think is the previous "good" version instead of 18.6.1 (which I had been running) work just fine. RX 480 card, by the way.
You could report this to AMD..this form asks for specific game(s)/application issues....and possible fix in the next round of drivers.