Had this on the beta 4 one time just after updating, just toggled BT off and back on and it got straight. Not had a problem since. Maybe drop the device and re pair it will help as there were changes to BT in this version (at least for the SE) so re pair may be worth doing.I get terrible stutter over Bluetooth since the update, it is basically unusable in my wife's car (2011 Subaru Legacy w. Blue Connect). She has a 6s+.
My Bluetooth works in my car, though with my 6s. Go figure. I might try resetting her phone.