Pre-Cueing: "USB sound card" mixes unwanted with Main output: "Built in output"

When trying to listen to a song in head set it’s also heard in the main output/speakers

djay pro 2 v2.0.11 on Mab book air with OS Mojave 10.14.3
Pre-Cueing: “USB sound card” (Plexgear USC-100)
Main output: “Built in output”
Cue/mix is all the way to the left
Split cue: off

Loading a song on deck 1
Fader to the right
pressing play
and finally the headphone symbol under deck 1

Sound is now played in headphones correctly but also in the main output left :frowning:
Same goes if I play a song in the main output it’s also heard in the headphones without Pre-Cueing it

Same problem when i use a blueooth headset instead of the usb sound card

I have also tried

running: “defaults delete com.algoriddim.djay-pro-2-mac” in the terminal

Deleting the app and installing again
including deleting settings folders but it looks like some settings are stored in the cloud…