When you switch to DirecTV, your problem may go away. However, if you just love debugging computer problems, here are some ideas.
Most folks complain about "judder", which is a jerkiness (or bounce) during motion scenes.... not during static scenes. They compensate by setting AMP (AutoMotionPlus) to Clear, or Custom/Blur 10/Judder 0).
Another thing they try is to set Film Mode to ON or Auto, which helps tame video jumpiness in movie transmission, and has been reported to help the crawl at the bottom of sports or news channels. Try these one at a time, and, if they don't work, switch back before trying something else, and before you switch to DirecTV.
Your mention of sitcoms indicates you may be talking about older shows. Often, broadcasters cut out frames to get in more commercials and there is no way you can get rid of the jumpiness. Old Murder She Wrote shows on Hallmark, etc., are pretty bad on this.