nope...ain't got that problem...my screen isn't flickering when i lock the phone/unlock the phone,it goes straight to the homescreen whitout any flickering like you said.,try to reflash/flash another rom...
i have the same problem...my screen turn off by itself and need some time to put in on again...like deep sleep,just read the page before this,someone tells a version of TWRP that works on OREO.