Telling Plex to ignore music files already processed?

hey otto! i tried a little experiment to temporarily bypass my issue due to using one flat directory as i re-structure my library:

i selected 3 new albums that i added but didn’t see their cover artwork. i then refreshed their metadata as a selected group. it took TEN MINUTES to refresh and add their cover album art. i repeated that experiment several times… ALWAYS TEN MINUTES!!

any explanation for this? is there some kind of timeout timer in the software causing this or just a coincidence of my environment? i have nothing running on that box except plex (2 ghz quad, 16gb ram, mycloud nas)

thanks otto!