I have a Galaxy S4 (ver 4.4, 5ghz N) and an older HTC Incredible 2 (ver. 2.3, 2.4ghz N). I recently had an issue where my S4 was sputtering once the screen was turned off. I know Android "relaxes" the wifi power when idling, and my signal at the time was lower than usual (I was outside), so I chalked it up to range issues. 

However, my usually-reliable HTC is now having issues as of recently. It too is having the EXACT same issues as my S4 where, when the screen is off, it begins to stuffer playback after a short period of time. Immediately, as soon as I turn the screen on, playback returns to normal. I can do this over and over with the same result (screen off, stutters, turn screen on, normal). This was all happening within close range of the WAP, so low signal wasnt an issue. No channel congestion either. 

Both devices are using "extreme quality". If I lower the quality, the stuttering lessens, but picks up again once I increase the quality. It really seems like Spotify isn't buffering properly when the phone is on standby, or buffering too much when the wif is in a lower-power state. 

The kicker is, Google Music works perfectly on both phones. I also don't want to adjust the wifi power, as it'll kill my battery. 

Did a recent update to Spotify cause these issues? At this point I'm unable to use Spotify on either android device and will have to switch to an alternate service, unless this is just a temporary, known issue. Thanks in advance.