Somewhere earlier in the thread I mentioned that wired CarPlay works fine. So it's not the car. This device is intended to simply replace the wire with a wireless connection.

So everything else in the chain (phone, car, CarPlay itself) are fine. And this is two different brands of adapter, one of which lasts longer than the other one before it goes Tango Uniform. The only common denominator is the fact that this is a wireless adapter to replace wired CarPlay, and that programming wireless shit is difficult and prone to bugs.