File thumbnails

This has actually been an issue I had with a previous site which is currently in the process of being updated. Previously it wasn’t an issue as all downloads used the same thumbnail however now each download has it’s own thumbnail (software logos).

Any time I update the file with a new release of the download it seems to lose the thumbnail and I have to re-upload it again. Is this normal behavior or am I missing something in the settings that is causing this?

Thanks!

http://ww.wp.xz.cn/plugins/wp-filebase/