Google once again changed the internals of the Android Bluetooth stack, and guess what: it breaks my phonebook app. It is no longer able to properly stop the built-in phonebook service.
Today I found out that the latest Android source contains a change which once again enables my app. I don't have an idea when that change will be published in an official release or if there may be new Android 8 firmwares in the future which don't contain that fix. Simply check if your car connects to my app, if not you'll probably have to wait for the next firmware update.
And these problems all happen only because Google refuses to add a proper Bluetooth SDP API to the Android SDK. So they work their way from hack to hack. Sad...