Field order issues with progressive graphics in interlaced project

I added some 25p progressive overlay graphics with alpha transparency to a 50i timeline. Footage is 50p as well so it all should be rendered out as 50i upper field first. It looks fine on my monitor with blackmagic intensity shuttle attached. But when I run it through QC i get some "wrong field order" alerts for those graphic parts. Those alerts are in the middle of the graphic, not at the start.. FCP has some settings like Field dominance override and Rate conform. But everything in Rate Conform Frame Sampling other than "floor" looks very jittery (nearest neighbour, frame blending, optical flow). Is there a problem using progressive graphics in an interlaced project in FCPX?