This sounds like my BT bug issue. When listening to anything over BT (Google Music, Pandora, I Heart Radio, Amazon, etc), if I disconnect BT before manually stopping in app whatever is playing (in other words, if I let BT disconnecting stop what is playing), the phone acts like the item is still playing and won't allow me to play anything else (basically if it has a play button, it won't work). I recently noticed this leaks over to notification tones not playing sometimes as well (but ringtones for phone calls don't seem to be impacted). Nothing will work to correct the issue except a reboot of the phone.
I have already submitted the issue to Motorola via the chat feature on their website. I ask that if you have experienced the issue to do the same so that it stays on their radar and the bug is researched and corrected.