Volume goes down in background automatically

[Leothury]

Plan

Premium

Country

 Brazil

Device

Lenovo Moto Z2 Play

Operating System

Android 8.0.0

My Question or Issue

 When I'm running Spotify in the background and open any other app the songs volume goes down (feels like 50% less) and the only way to turn it back to normal is to close Spotify and reopen it. The Android volume stays at 100% but it's like the Spotify app is the one lowering the volume. I didn't find any option in the configurations to fix this and I did not have this issue with my last phone a Motorola X Play.

Can anyone help find a fix for this issue?