The Plasma will be de-interlcaing anyway so you will only be seeing a single field. So field order cant be the issue.
Also reading back in the first post, you said that you were separating the lower field but then rendering with lower. You should only render with fields if you have not sepated them, Other wise its like de-interlacing you footage and then re-interlacing upon render.
So I would: In the interpret footage settings, set it to separate lower field first, then when you are good to render, render it out with no fields at all. you will have a progressive movie so should not jerk at all, and will also look more filmic.