Compressor showing white lines after export via FCP.

Hi all I have used compressor to export my movie and before doing so I cropped in compressor to get rid of pillar box on the sides. There were no pillars at the bottom but after exporting 8 bit uncompressed I am seeing a white line appear at the end of the video. I tried exporting also with different settings H.264 but still see it. Does anyone have any clues as to why this is at all please. Sorry if insufficient information here but new to forums. Thank you. Ryan.