When I'm in my car everyday on my way to work, I have my android phone (Lollipop 5.1.1 - Spotify last version) playing downloaded music on spotify using aux-in (not bluetooth). I have no Internet connexion but it's ok songs are "downloaded". But I don't know why, some songs keeps pausing randomly. 

When it happens I have to press play button everytime it stops (it can stop a few times on one track). If I listen to the song again, the song pauses at the same positions. But if I listen to the song at home/work using wifi, now it's playing fine.

It's like songs can get corrupted over time. Because it happens randomly to songs that were playing successfuly before.

I found other topics about that specific problem (or similar) but all are set to solved and solutions were not helpful. 

I tried to reinstall. Ok it works, but few days after some songs get corrupted again. This does not fix the problem. It happens again randomly.

I recorded that problem to show how annoying it is. https://youtu.be/CaC9UY6k7Z0

Problem starts at 31 sec and occurs a few times on the track.