I've had a stuttering problem with my 622 on HD recordings for a while now. As far as I can tell, it only happens with OTA. At first I was thinking it had something to do with a temporarily weak signal, but it happens even on my NBC channel which is always in the 90's. I also don't notice any pixelation as you would expect to get from a weak signal.
The problem is really annoying when I'm watching a football game that is still being recorded. If I let the game record for, say, an hour, and then start watching it, it will sometimes stutter, and then skip to live TV. So suddenly, I know what the score is going to be at or near the end of the game. Argh! I go to great pains to not hear the score of a game I've recorded, so this REALLY annoys me. It's happened more than once.