Screen casting problem in galaxy S8 after oreo update

There is an update for screen casting feature in the oreo version of android in S8, that screen goes dark while playing video.
Feature is good but when screen goes dark video streaming is not seemless. Video stucks while playing.
When i wake the phone up again by swiping the screen, it sream flawless. But screen goes dark automatically in few secs, whi h makes the video casting experience awful.
There is not even an disable option for this feature.
Please advice solution for this problem