Hey Dan,
This reads to be common and, not unique to CMF rather, something some folks experience with Google Maps generally. I’d follow these instructions on Google Help Center as a first pass. I’d also switch off battery saver (if on) and do-not-disturb (if on) while also, uninstalling and reinstalling the Google maps app. Failing the instructions above, consider following these steps
1. Connect to car via Bluetooth
2. Navigate to your Bluetooth settings
3. Select Connected Devices
4. Select the car you’re connected to in Bluetooth Settings
5. Deselect Media audio
Does that fix it? I’d also recommend submitting this as a bug to Google.