Premium running list stops at random

[WilliamOffline]

 I created runnng lists with various speeds based on the BeatRunning albums. It helps me train running pace.

E.g. 170 BPM list: https://open.spotify.com/user/williamsiemons/playlist/0eR0mvutKvk0AVBC1jXxg3

Unfortunately these lists stop playing on the Sony Walkman NWZ-F886 at random between songs (after 1, 2, 3 or more sorngs).

I had similar issues on the Sony Walkman ZX-2 and hardly use Spotify on that one due to all issues I had past years with spotify (back to flac and mp3).

The last thing you want when running concentrated is to grab your walkman and start stop the list. So as I am typing this I am recording a shuffle play back with Audacity of the playlist to convert to MP3 so I can have a reliable playback during running. Ridicoulous solution, but spotify does not have a better work around.

All problems I had and have are on premium off line usage unrelated to which device that is (MP3, phone or tablet). 

I hope Agile at Spotify does not imply that robust and reliable premium playback is indefinately procrastinated for more fun user stories.