Why is KDE connect interfering with bluetooth audio streaming/receiving?

After I enabled KDE connect in NixOS 25.05, audio cannot stream from the phone to PC over bluetooth like before.

I often connect

Phone --> PC --> Bluetooth Headset

Both via bluetooth, and the PC would be able to merge audio from phone with PC audio. This has stopped working reliably recently and I think it’s because of KDE connect.

Running kquitapp5 kdeconnect or in my case:

nix-shell -p libsForQt5.kdbusaddons --command "kquitapp5 kdeconnect"

Fixes my issue temporarily.

How can this be debugged?