Picture goes black briefly on Apple TV. Why?

This question was posted previously and turned up when I searched. The response to the previous question was that the trouble could be caused by Dolby and it should be turned off. Also could be the HDMI cable. My system has been connected without change for two years yet the problem occurred only recently. The Apple help line tech said only the cable and insisted it is not the software. The cable is a high quality one and as I said has worked for a long time. I tried a brand new HDMI cable after trying the Dolby setting. The trouble was still there with the new cable. I then swapped the Apple TV cable with the cable from my DVD player. That solved the problem at least for now. Same cable brand and same age. The cable that was connected to Apple TV works just fine with the DVD player. What is the real problem here? Why is the Apple TV such a problem with HDMI cables when other devices are not. And why now? In my view this is an Apple problem probably related to some recent update. Does anyone understand this?