I have what may be a defective device. After about 10 minutes of turning on the TV and the attached Roku 3921X the picture begins to flicker and turn on and off every few minutes. I initially thought it might be the TV but since it is attached to a smart TV I can switch to say Netflix on the TV to test the flicker. So I can switch back and forth once the flickering starts and it does not occur when switched to the TV's Netflix channel. Any thought on how to definitively determine if the device is defective.