I also am getting a weird artifact on ABC. Whenever I watch or record something from ABC every now and then I will get this horizontal line artifact in the upper 1/3 of the screen. It lasts for about a little less than a second, but this just recently started happening in November and is a minor annoyance.
Funny you should mention that. I too have seen a yellow line appear at the top edge of my ABC local. Unlike your case, I have to change channels to get it to go away.