interlace effect moving image

Hi,

I edited a one minute video file in FCP shot with apple prores 422 HQ 1920x1080 footage.
In the project there are two shots in which a movement comes with an interlace effect.
Although the material is not shot interlaced right? (It doesn't say 1080i).
I've read a bunch of articles about interlace and so on but in this case interlace shouldn't be the problem right?
Does anyone have a clue why some movements seem interlaced? is this a FCP thing?
thanks so much,

sara