CarPlay. Receiving call, can't hear the caller.

Iphone 7 updated

CarPlay in Subaru Impreza

I listen to the radio.

Phone call comes in, I can accept it.

The screen switched back to the radio screen (Subaru) and show the ongoing call (timer counting).

The person on the other side talk to me, but I can't hear.

I have to pull out the phone choose "speaker" in the list of sources, and have the conversation through the speaker of the phone.

Or

I put the call on "hold" (accessible within the radio screen from Subaru), then toggle it back to "untold" the call, and then I can hear.

Is there something I miss ?

Could this have been related to iOS12 ? Not sure, I can't remember when this started.

Thanks.

Oli.