I download lots of MP3 podcasts to listen to later with the built-in Windows 10 audio player, Groove Music.
Sometimes, not all the time, but not rarely either, a podcast ends and I doubleclick on another in an Explorer window but instead of it starting right away, I get the crawling dots in Groove Music as if it's pondering its next move. The title of the next podcast is already displayed, so the MP3 has somehow started to load into the player, but the slider with the current and total playing time is not there yet. That's where the crawling dots are.
Looking at Task Manager, Groove Music is nowhere near the top. What is it waiting for?