Issue: Under certain circumstances the notification will not appear. When this happens you are unable to use bluetooth controls. Additionally Spotify does not appear as a choice of music player or under power saving settings for apps.
Timing: The issue started about a week or two ago.
Device Info: I am running Android 6.0.1 on a Samsung Galaxy S7 Edge G935W8 (stock, unrooted) with the RWC CSC.
Trying to Replicate: I understand the developers need to replicate the problem to fix it and that has been quite a challenge for me as it seems to appear under different circumstances. I don't how I did it but I was able to capture the issue with a screen recorder (it does seem like swiping the app away, than launching it again, playing a song, and then pressing the home button is what caused it this time).
Now that I have concrete proof it's up to the developers to find out why. I feel I've done more than my fair share as a longtime paying customer (once again this happened at the worst time because I deactivated Facebook so I lost Spotify access so i just look like some random trial account pleb). Also I do want to note that while it took me almost 2 minutes to make it happen now, it has happened 3 times in a row while driving.
Image of app not appearing under power saving: http://i.imgur.com/iL9vrln.jpg
Image of app not being a choice as music player: http://i.imgur.com/X1aovJ2.png
Video of the notification not appearing (took over a minute to make it happen): https://drive.google.com/open?id=0Bw7x-8_1Mrf9RGZjV190R01HUUE
I posted this as a reply but it is deserving of its own post IMO since I put the work into taking these screenshots and recording it.