VLC 4: Thumbnail missing after re-scanning library for no reason

After re-scanning the library (the thing that happens when you re-open VLC), after the scanning finishes, sometimes previously present thumbnails go missing for no reason whatsoever as the file was not changed so there is no reason to do any change to the thumbnail, let alone remove it completely.

Note on the screenshot the thumbnail for 20 000 BC is missing, while when I filed #25875 it was still there just moments before.