Artifacting on top line when cropping source and transcoding

Working with AME to to transcode some files from .mov 720x486 Lower to H264 1920x1080 upper so they'll play nice with our server. I'm cropping out the overscan from the source as seen in the first image, but when I output it I get a soft edge as seen in the second image. The only way I can get rid of the artifact is to rewrap it as a .mov lower. If I export as .mov upper or H264 Lower I still get it. Any ideas on how I can fix this?