Well it's good to know it's not just me. Maybe a radio update will help at some point.
I did wonder, but I've used this headset with probably 7 or 8 different phones. It's always been a little crackly at times, but nothing like it is with the 6P.
After doing some phone reviews, I finally got to come back to my own phone, which I'd decided would be the Note 5. A few days in I was getting some pretty bad battery life, coupled with the annoyance of not being on the latest Android version, I figured I'd switch back to the 6P. Already (helped by these BT issues) wondering about switching back.
I wouldn't mind if WhatsApp could work across two devices... That and Android Wear needing a factory reset each time.