Thanks for keeping us updated. My problem hasn't been resolved and I am sick of them saying "its an Apple " issue. No- it isn't- because my previous car, which wasn't a Lexus, WhatsApp worked absolutely fine.
At least your technicians are trying to do something about it. My local dealership is useless - I think I understand more about the problem than they do. Also I am not sure what they are saying about the pre-August software malarky as I have had my car two years and WhatsApp has never worked properly, becoming even worse when I upgraded my phone.
I have wasted countless hours trying to get WhatsApp to working the car and still not much further on. I have found, however, by my own deliberations, if I ignore Siri when I see I have a WhatsApp message and just press "receive messages" on my screen Siri will actually have a stab and telling me what they are, but if I try to reply, it is a complete waste of time.
I shall await your further news with interest.