I have been on DISH for almost two years now and I have same problem occasionally on our local ABC station here in Raleigh area. There is nothing you did, or can do except complain to DISH. It comes and goes here; makes me wonder what changes in the feed to trigger it. But when you see it, it drives you crazy.
Between this and audio blips (on recorded shows from same ABC station), my wife is ready for us to switch back to Directv...which we had for 10 years ad never had such problems.