Black flicker in viewport and PIE (Mac OS 10.12)

Hi! I got this issue on opening project on our new 2017 iMac 21,5 for iOS development and deployment. Radeon with 4gb vram.
The old 2012 iMac does not have the problem. Both Run High and engine 4.16.3
A new 4.16 fps vanilla project I just created on the same iMac shows no flicker!