iOS automatically kills applications that run in the background for too long. I tried implementing some code that bypasses this restriction but it sounds like it's not holding on your devices.
Can you try opening Info.plist inside of the AppRadio app bundle and add audio to UIBackgroundModes? You can use iFile to modify the file on your device.
It should look like this:
<key>UIBackgroundModes</key>
<array>
<string>external-accessory</string>
<string>audio</string>
</array>