Picture freezing for a few seconds and then continues

I have had this problem for a couple of months. Randomly the picture will freeze. Maybe once every 3-4 hours. It stays frozen for a few seconds, turns black, and then continues. If I playback the DVR a few seconds it shows slight static at the point where it froze but does not freeze again. I have phoned many times where their suggestions do nothing. A service technician came out twice. The first time he contacted another technician working nearby and they discover a board on the line was fluctuating in voltage and they fixed it The problem still continued. A couple weeks later the same technician came again and found nothing wrong on the line. He replaced the box (which was the second time in a month). He also replaced the HDMI cable. The problem is still there. What can I do? I do not seem to have a problem with internet which I use much more than the TV and uses the same cable.