Regenerate Video Preview Thumbnails for Individual Movies

Perform an Analysis on the Movie/Show (Show or Season level - I think).
Pre-play Screen (Show Level) - under the dots.

For the Thermonuclear approach (if somethin’ fishy is goin’ on) - Plex Dance - that’ll get it (or we’ll find out why if it doesn’t):

In some cases if a Merge has occurred with two movies that are similar enough in their makeup - Plex will share the thumbs. Usually this works out fine - Usually.

If the run time is different, you will need new thumbs - in that case, Split, Fix Match on one of them and change to the other agent. That should tell Plex this one is Brand New and will require new thumbs - Usually.

There’s a few ways to skin that opossum - that’s one of them.