Mine has been doing the same thing. Sometimes on the left, sometimes on the right. It works in conjunction to the screen TVbrightness/PictureMode. If I set to Normal/Normal, all is ok. If I raise either 1 of the 2 settings to a brighter screen, such as bright or vivid or enhanced, I get the flicker. Also, changing the backlight level higher will cause it as well. Annoying, but will put up with if for a while, until it gets worse or goes out.[br]
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If I have to replace it, will go back with the same TV I guess. TCL Roku 55” 4K.