One particular movie won't hold onto its thumbnail

[cujimmy]

All my movies in iTunes have a dvd cover image I've downloaded. However, one particular movie just won't hold onto it - after pasting it into the info box and clicking ok, the thumbnail will be there and then, a second later, vanish.

How can I solve this one?

 

[MRiOS]

Try using a program like MetaX to write the image into the actual metadata of the video. I've done that loads of times and it always keeps the cover thumbnail.