I have a large library of animation shorts which I have spent a fair amount of time creating thumbnails from screengrabs of the title cards. They displayed very nicely, properly cropped to the size of the image. Suddenly, however, they have begun to be displayed in a vertical aspect frame with large letterboxing on the top and bottom. On some thumbnails it appears that MC attempted to average the letterbox color to match the card, but most of the letterboxing is black.
Why is this happening all of a sudden? The jpg images that the thumbnails are being created from are unchanged. I cannot find a parameter for thumbnail information to change the aspect. Recreating the thumbnail from a new screen grab doesn't solve the issue.
I know it sounds like a minor thing, but I enjoy browsing the shorts via the title cards and now I can barely see them shrunk with the thick black bars in the thumbnails.
Any advice?