Videos won't play when bluetooth connected, ritual needed to make it work
Bluetooth on Linux always has been a pain. I would suggest either doing a fresh install of Zesty, buy a new Bluetooth headset that can just be used with the Ubuntu device, and/or buy a new wired headset/phone.
I have similar problems with Bluetooth.
Luckily pylover has turned the ritual into a program.
See here:
https://gist.github.com/pylover/d68be364adac5f946887b85e6ed6e7ae
This program generally works for me.