TL;DR:  While listening to music through headphones, unplugging will cause music to continue playing through speaker

Many instances when music is playing through physical headphones or bluetooth and is then disconnected from my phone's (Nexus 6P) audio, Spotify will then switch over and continue playing music on my device's (Nexus 6P) speakers. Not sure if this is on Spotify or from Android 6.0 (Marshmellow) but this is completely unacceptable on either end. This doesn't happen 100% of the time and I'm not sure what the conditions are for it to happen. 

Another problem is the floating notification. Usually exiting out of Spotify with task manager or pressing the X on the floating notfication will stop the music and close Spotify. However, a good number of times (not all the time), Spotify will continue playing and I will be forced to reopen it in order to pause the music. 

Any solutions? Not even sure if this is the right place to post for help. If it's not sorry in advance.