I have a Roku Express 4k. The Roku gets it's power from the tv USB port. Initially it has worked fine, but now every time we turn on the TV and choose something to stream, the video is black even though the audio is working. To get it to work I have to unplug the usb power from the tv and plug it back in. The Roku turns back on, I can choose the same video, and it works fine. The Roku will work normally until the tv has been turned off and therefore the Roku is off, and the next time we turn it on we have the same problem again.