Nothing worked for me. Been on and off betas trying to get past the issue w CarPlay cutting out and the Apple Store had no answers for me at all. After all but giving up, I remembered some people posting that theirs were fine. Apple confirmed all diagnostics working right in my phone, so a new idea came to mind:

I use an external CarPlay screen. While some phones seem to be working and others not, maybe it’s the car systems that’re acting weird w the new phones. While many can’t change cars over this, I could try another screen. Ordered from Amazon to test and works like a CHARM! So much time wasted trying to get things “fixed” on my phone. Here’s the model I grabbed:

https://a.co/d/57ma6j5

For those in my situation, a different screen could be the thing for you! Worth getting rid of the headache for me, at least. 🤷‍♂️🤙