I was having all kinds of Bluetooth issues with my Nexus 6p and Toyota 2015 Prius V. Podcast would constantly disconnect from Bluetooth. GPS sound would stutter. Phone calls were hit or miss whether Bluetooth was still connected.
I was on 6.0.1. I recently received Google's January security update. Since receiving that update, I no longer have any Bluetooth issues. Everything works as it should.
I don't know if Google fixed something with this January security update, but I am happy again.
The January security update did not fix the problems with my Nexus 6P and 2015 BMW. If anything they're worse.