I use Spotify with Garmin 255 music
If shuffle is set to yes the music is not shuffling.
Perhaps it is how I play music and start an activity.
I select the music play list using the left center and left lower button and then exit back to watch face then press top right to select the activity start and then I press the play button on my bluetooth headphones.
Is shuffle working for others? Or is it how I am getting from playlist to activity starting?