Autounlock not working, when using Headphones

My Nuki 2.0 wont do anything, when I am using my Bluetooth Headphones. My Phone can also do Bluetooth 5.0 (S20 FE).
Without the Headphones connected, it works as it should.

Afaik, Bluetooth 5.0 should be able to work with more then just one Device at a time.