Tried every conceivable player, Spotify, YouTube Music, YouTube, Apple Music (local files), Soundcloud and more, all of them leading to the same thing, via USB+CarPlay the sound get normalized somehow but if using AUX/Bluetooth, works normally.

> Maybe it’s trying to split the output into more than two audio channels when in CarPlay mode?

I hope so, most of what I play is stereo, and works fine via AUX/Bluetooth.