I have a XV6800(replaced XV6700 WM5) and even before upgrading to any ROM my Bluetooth was crap. My xv6700 worked much better and that wasn’t great either.
I have the Panasonic link to cell phone system and the 6800 would only make a connection to the system but I could never dial a pin or talk for more than (10 secs) without it disconnecting. My jawbone headset sounded like garbage also........
UNITL!!!!!!
I found this little gem.
http://jetwaremobile.com/
My Panasonic link to cell works great and my Jawbone is crystal clear!!!
Give it a try, what’s the worst that could happen your Bluetooth works the way its supposed to.