As someone who knows a little bit about computer science, I believe the issue is that multiple instances of spotify are allowed. Maybe this is intended in Linux but it came to my attention since it is not allowed in other platforms (i.e. Mac OS X).
How I noticed it (in case it helps you with debugging):
(1) I was using the app.
(2) Closed my laptop's lid. The OS went into suspend mode.
(3) Came back and search for the spotify app and ran it again. The existing running app was not replaced, it was simply opened as a new instance.