Sounds like both problems are related. My understanding is since the frame rate isn't as fast as it should be, the equipment/decoder is probably trying to update/buffer the image to the latest frame every few seconds, resulting in the jump. The glitchy image could also be related. I have to hook up my Youngstown antenna and take a look for myself. I can't get WYFX, so analyzing it on WKBN 27.2 maybe difficult due to the extreme compression.
HD Radio: An Audiophile's Worst Nightmare.