Well, there could be a few things in play here.

One is that many of the content providers (cable/sat) can often compress the signal as it is distributed. The other is that jerky motion can also be attributed to a weak signal. Since the units don't have "static" like the old analog televisions do, frame freezes occur instead with a weak signal.

Now, if the signal is constant, and the AutoMotion Plus is causing a jerky or "watery" motion, it may be that the signal is being over processed, in which case, the best remedy is to adjust the AutoMotion Plus setting.

Keep me posted.