Please can you try just opening the launcher on Bangle.js, then connecting and seeing if you can download via GPS Recorder?
I just generated a track>10 here and the download works, and it seems that the code you pasted above works perfectly (which is the exact code the GPS Recorder downloader uses). So all I can think is maybe the clock face that you're using is printing some data to the console or delaying a long time, and that's interfering with receiving the track list.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
Please can you try just opening the launcher on Bangle.js, then connecting and seeing if you can download via GPS Recorder?
I just generated a track>10 here and the download works, and it seems that the code you pasted above works perfectly (which is the exact code the GPS Recorder downloader uses). So all I can think is maybe the clock face that you're using is printing some data to the console or delaying a long time, and that's interfering with receiving the track list.