2015 Sierra SLE - does anyone's "shuffle" actually work for USB audio?

Hey!

Just wondering if I am doing something wrong (file type, etc.) because shuffle seems to be absolutely useless at actually shuffling my audio.

I tend to use a USB stick to play audio from, and shuffle will always revert back to the same starting song and then continue forward with the same songs, always following in the same order. I can trick it for a few songs by selecting a random track from the long list, or by hitting back/forward a bunch of times, but after a couple (seemingly) randomized tracks it always goes right back to the same starting point and carries forward from there.

It's like it has created a "shuffled" list in its brain, and not only holds onto that list as default, but will go back to the start of the list if its forced off of it for more than 2 or 3 tracks.

I would love to figure out how to get this to work - its incredibly frustrating to have thousands of songs to listen to and constantly hear the same 5 or 10 every time I drive.

Thanks for any help you can lend. Cheers.