Sorry - that jerkiness that did exist in DivXtoDVD simply is not there when converted with ConvertXtoDVD.
Engine is totally re-written and it does proper pull-down.
So, without more information there is no explanation to you.
Only thing that might affect is your system codecs and DirectX; if they are not up-to-date then problems might arise. But you should see that same effect when viewing un-converted file on PC.