Video preview thumbnails for existing media?

[jonomite 29]

I recently enabled the "generate video preview thumbnails" option in my movie library. I set it to run as a scheduled task and when media is added. I've confirmed that this feature is indeed working with newly-added media. However, it doesn't seem to be working for media that was already in my library. I've run both the "scan media library" and "thumbnail image extraction" tasks in my scheduled tasks menu, but that doesn't seem to be doing the trick. Am I missing something?

[Luke 42079]

Hi, have they been created?