CarPlay Nav Apps not decreasing Music App volume & can’t adjust Nav App Volume

In a recently acquired vehicle (2023 Toyota Hiace), with my updated iPhone 15 connected by cable, I’ve noticed Google Maps doesn’t ‘dim’ the volume of Spotify Music when reading out Turn by Turn (TBT) instructions.

I also can’t adjust the TBT volume when it is read out - The volume only adjusts the Music.

The same thing happens with any combination of Google/Apple Maps & Spotify/Apple Music.

However, Spotify/Apple Podcasts work as they should - TBT pauses the Podcast & then resumes automatically.

If I connect the iPhone by Bluetooth (no CarPlay), then it works fine, with Music dimmed during TBT instructions.

I drive a lot for my job, so this is very frustrating & pretty dangerous as I need to take my eyes off the road to see where to turn instead of being able to hear the TBT instructions.

I suspect CarPlay & Toyota head unit software are to blame.

Please have this fixed soon as it makes for an uncertain/unsafe journey.