Nexus 5. Android 4.4

Here's exactly what happens:

- a song ends

- the next song starts playing (progress bar and everything) but you don't hear anything

- just now I was away from my desk for a few minutes and when I came back I heard nothing (left it running) so I unlocked my phone, and saw that it had reached the end of what I assume was the "silent song" (I'll just call it that), and it didn't automatically go to the next song

- sometimes forwarding to the next song or going back to the previous song causes that song to play silent as well, but sometimes this fixes it

- sometimes you have to restart the app

- sometimes it happens after 1 song in a certain playlist, sometimes after 3, 10, whatever, seems random

- it happens whether or not the phone is connected to a computer

Plenty of topics with this title, all over the forums, different OSes and devices.

http://community.spotify.com/t5/Help-iOS-iPhone-iPad-iPod-Touch/Spotify-stops-playing/td-p/439160

http://community.spotify.com/t5/Help-Android/Music-stops-playing-randomly/td-p/486584

http://community.spotify.com/t5/Help-Android/Spotify-stops-playing-music-randomly/td-p/349488

http://community.spotify.com/t5/Help-Desktop-Linux-Mac-and/Spotify-suddenly-stops-playing/td-p/44443

http://community.spotify.com/t5/Help-Desktop-Linux-Mac-and/Music-stops-playing-after-a-song-but-show...

http://community.spotify.com/t5/Help-Android/Spotify-randomly-stops-playing/td-p/157908

All of these.

An educated guess: ram issue. perhaps there's something failing in memory allocation? garbage collection? I dunno.