I mostly use Spotify on my Windows 10 desktop and on my iPhone 6S. I had been listening all morning on the desktop and had queued a couple of hours of music. Then I went to another room and switched playback to my phone. The song that was currently playing on the desktop started playing on my phone, but the tracks I had queued in the desktop app were replaced by the playlist (not a queue) that had been playing on my phone a few days ago. When I returned to the desktop, I found my queue was replaced there as well.
I'd prefer to have a single, unified queue for all devices associated with my user ID, but at the very least, can the Spotify apps prompt me to choose a queue when switching devices rather than wiping out what I had queued?