Hello! I am experiencing the exact same thing. Especially the outline of a selected geometry flickers in most places - that is the blue or green lines are flickering. My project is a fresh install of 4.17, with a ground and a geometry box and sphere.
The flickering goes away when:
- I switch from additive to subtractive.
- When i press a menu, like the settings, play or launch-drop down menus in the top of the viewport.
Did a fresh install of video drivers, dont really understand the issue. I have a Gtx 970, i5, UE is on an SSD, Windows 10.
Please halp!!