Sorry to hear about your Bluetooth issue. Unfortunately that is a very common issue after Android OS updates (at least it was on Moto phones for the 10 years I owned Moto phones). In many cases, the Bluetooth permissions and authentication protocols changed with the new OS and you have to setup the device / vehicle as if it were new, so the new permissions can take effect. You can report bugs at the link ggrant3876 provided. You can also ask for help at the Google community, at:
Google Help
Don't expect to hear anything from a Google employee, they don't respond at the bug report site and rarely respond on the help forum. The help forum is full of fellow Android users and volunteer administrators (kind of like here). If you are a Google One paid subscriber you can use the direct chat feature to talk directly to a Google tech support rep. In any case the only thing you will probably hear is the standard troubleshooting for the issue you described:
* Open Phone Settings > go to Bluetooth (or Connected Devices) and forget / delete your vehicle
* In Phone Settings go to Apps (or Apps & Notifications depending on device) > All Apps > click the menu to select Show System Apps > find Bluetooth and tap Storage & Cache > the select Clear Storage and OK / Yes to any prompts. If you have an app named Bluetooth Share, repeat the steps and clear data for that also.
* Restart your phone.
* On your vehicle, find the option to Remove / Delete your phone from Bluetooth (or Connected Devices) Settings menu.
* When both are clear and have no record of ever being paired start the Bluetooth pairing process as new. Pay attention to permission requests on either screen, ensure you allow all permission requests or any other security type of prompts. In many cases we miss a prompt and the whole pairing process is no good.
Once they are paired again, hopefully the Bluetooth connection is stable again and works correctly. I had to do the above more times than I can count over the 10 years I owned Moto phones, and it fixed weird Bluetooth issues every time. Hope that helps.