Please file a support ticket and provide me with your ticket number
Ticket number: 8200830802
Thanks,
Ryan
Solved!
First I installed the Windows October Update that was released yesterday and tried the 18.Q3 driver again. Same blinking mixed reality display issue.
Then I noticed AMD release a 18.Q3.1 and the problem is no longer there. Hurray! Did some VR tests with the mixed reality portal and Steam VR and no crashes or weirdness so that's great. Thanks!