CarPlay Pioneer SPH-DA120 and switching from FM to CarPlay automatically

I have the Pioneer SPH-DA120 running CarPlay (Latest Firmware 1.11) with IPhone 6S running 10.1.1.

Everything is working well with my iPhone and Pioneer SPH-DA120. However...I now have the problem that if I switch to FM/AM radio on the Pioneer. the unit switches back to iPhone- Apple Music after about 2 minutes without me touching anything.

I have tried:

1 Changing the lightning cable.

2 Switching off WIFI on the phone.

3 Turning off background app refresh on the phone.

4 Quitting Apple Music while the radio is on.

5 Turning Bluetooth off

6 Rebooting the iPhone.

I have the latest firmware on SPH-DA120. iPhone is on 10.1.1.

If I switch back to Radio again after it has changed me to iPhone/Apple Music it will do the same switch back in another 2 minutes.

I would like to find out what is causing the Radio to switch to CarPlay/Apple music.

The Apple Music App is not playing in the background and I have even tried quitting the Music App from within the phone but it always switches from Radio to Carplay after about 2 minutes.