Fluctuating volume in car

[driekvds]

Spotify Premium

Country: Netherlands

OnePlus 6, Android OxygenOS 9.0.4

Volkswagen Golf 7, 2018 model

When I play music in the car, either via Bluetooth or Android Auto, the volume seems to fluctuate a lot. It seems to happen during the same parts of a song over and over, as if the song was misproduced. However when I play over Chromecast at home there's no issue. Also on the phone itself the issue is not there.

Phone was on silent mode, no navigation on. It happens when I don't receive notifications.

It's very, very annoying. If there's a solution I'd love to hear it.

[driekvds]

Also happens in a different car with AUX connection.