Fortunately that’s not how it works when you have all the access points controlled centrally, like with unifi. Yes there is limited frequency space, but this is much less of an issue on 5ghz. There will also only be one ssid, and handoff between access points is pretty seamless.
3-4 is probably overkill, but the attenuation situation sounded pretty dire. I run two in my house for redundancy mostly, just standard American stud and drywall construction.
If you have the ability to easily add wires, I would go with a system that allows you to wire everything together, rather than depending on a purely wifi mesh. Personally I’m running unifi ceiling mounted access points for this. They run on power over Ethernet, so you just need to get one cable to each. You can control them with their free software controller if you are into that, or something like their dream router.
Run 3-4 of those access points placed throughout the house and you’ll never have a weak signal again.
Why does this only work in Hondas? What about this cares about the car?
If a controller is still connected (Bluetooth?) it may be a controller order issue, you can try reordering them.