Default Kitkat 4.4.2 Fullscreen Video Sometimes Show Blank but Has Sound

Hi, After upgrading my Wifi only tablet to 4.4.2 sometimes the video fullscreen just shows black screen. I hear sound but no video and occasionally there are some pictures flickering very fast but still unwatchable. I usually just reboot my tablet and thing seems to be sorted out. It happens pretty often.
Does anybody know what the issue and how to fix it for good?
Thanks