Had this problem for a few weeks now (latest firmware update didn't fix it). Every now and again, I've found my music won't advance to the next track. I have 1431 MP3 tracks currently on my watch and usually just randomise the whole collection when playing them rather then using a specific play list (though I do use a single massive Running play list to decide what songs to upload through Garmin Express). At the end of a track, sometimes the next track just doesn't start playing. It shows up on the screen with the timer stuck at zero. Pausing and unpausing doesn't make any difference. The only fix is to open the music app (long press of bottom left button) and skip to the next randomised track. Usually happens every five to six tracks, but sometimes it seems to get stuck in a rut and seems to happen with every second track. Nothing wrong with the MP files themselves - they play fine on my PC (iTunes) and iPhone (Cs Music). Gets really irritating because I end up running with the music app open the whole time and then I can't see my pace or power. Also a couple of times, at the end of a run, if the music app is open, stopping the run ends up just stopping the music and I end up with a load of stationary time recorded before I notice. If it makes any difference, the headphones I use are Aftershokz Aeropex and I usually run with my Stryd footpod connected.
Is this an issue with the number of MP3 tracks I have (hopefully not, still plenty of space to add more)? Is it a problem with having two bluetooth connections (headphones and Stryd) at the same time? Or is it just a glitch in the latest two firmware versions?