Found the malfunctioning part.
When I turn off the Show->Lighting Features->Indirect Lighting Cache, blink disappears.
When turn on this feature, blink starts.
Now I’m digging into code to locate the problem. If you are bothered by this problem and can not wait, just tun off Indirect Lighting Cache for now to finish all the job unrelated to Indirect Lighting Cache.
Hit play, if renders still are blinking. Then you can you console command(press ~, then you can input command):
ShowFlag.IndirectLightingCache 0
then blink stops
Collateral damage:
After I rebuild lights, blinks starts again. However console command does not work here. And it won’t stop until I reboot UE4 Editor.
I don’t know why, maybe light build progress will build with indirect lighting cache. So the viewport will ignore the show feature settings after it apply the result of light build.
Hope I can find the real solution in time