Ok folks, I had another crack at this and fixed it (for my situation anyway) it seems to be Android Auto induced - this is what I did: Uninstalled Android Auto Unpaired phone from car Cleared Bluetooth cache, removed car pairing from phone. I THINK THIS IS IMPORTANT - While in Bluetooth settings on phone and with Android Auto still UNINSTALLED I went to Bluetooth/Advanced setting and switched Ringtone Sync OFF Re-paired (via Bluetooth only) phone with car - tested and it worked Connected car USB cable to phone and allowed the phone to promptme to re-install Android Auto - tested and it worked. Since I did the above it has continued to behave itself. I belive the two most importatnt things are: reinstalling ANdroid Auto and switching off Ringtone Sync. I have noticed since I fixed it that I went back into Bluetooth/Advanced settings and the Ringtone Sync switch is disabled with the following message: "Not supported because Android Auto installed" Good luck.
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I also own a Mazda BT-50 with the ALpine Head Unit and when I upgraded my S9 to the latest Android I got the same problem. Same as teh other Mazda owner - when I hang up the ringing stops. I have tried: Unpairing - clearing BT cache - repairing Unpairing - resetting head unit - repairing Neither of these worked - this continuous ringing happens both through Android Auto and when just connected via BT.
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