I think it might just be a 5.4 bug because it doesn’t happen in 5.3 with the same project. When running the movie render pipeline in realtime, all UI will flicker but ONLY when running a build/standalone. The video is of a brand new project in 5.4 with only epic’s built in things in the scene and it happens. Even if I just have UI on the screen and don’t use the preview window, it will flash that. It seems to be based on each time it changes a frame to render.
I first noticed it with my project when I upgraded from 5.3 to 5.4 and it started to happen. I’ve been messing with a bunch of settings for a few days and nothing seems to help. There are no errors in the logs and I’ve even tried to fix some warnings it talked about and still nothing.