This is caused by "Volume Levels" option.
For some reason listening for volume events makes Android think app is used on another device. Probably this is something related to Spotify lawsuit, Google volume key fiasco, and their patches around that.
- on Samsungs, the Samsung Sound Assistant (free app from Samsung) Volume step option works in Poweramp automatically without use of Volume Levels and it allows up to 150 volume levels everywhere in the system
- on other devices, the Volume Levels should be disabled for to avoid this issue with Android Auto