CarPlay navigation is not accurate on two cars and two different iPhones

Hello.

I got my gf a new iPhone 15. But the Carplay navigation is crazy, with the blue arrow randomly jumping around and giving wrong instructions (sometimes dangerous ones). This happens with Apple Maps, Google Maps and Waze. Also, this happens with our two cars (a Pioneer and a FIAT Uconnect).

We thought it was a problem with the new phone and tried her old one, an Iphone XR. Guess what? The old phone is displaying the same behavior.

Check my picture (it's in ptBR btw): the blue arrow is not at the yellow X where it's supposed to be.

My Android phone is fine with these stereos, and both her iPhones can navigate normally while not connected to the car.

Any tips regarding this issue?

[Re-Titled by Moderator]