Okay. Are you sure the original footage is lower field first? If not you can check this by 2x clicking on the file in the Project window (with the Option (Alt on PC) key held down), this will open the footage window. Go to a part of the footage that has some movement and Command (Control on PC) click the right arrow key on the keyboard. If the interpretation is correct the footage will move forward each press. If the interpretation is incorrect the footage will jump back on one frame then forward on the next. Once you have determined the field order you must render using the same field order. Does that help?
JD
John Dickinson
Motionworks
https://www.motionworks.com.au