I just switched back pulseaudio with pamac remove --orphans manjaro-pipewire pipewire-media-session pipewire-alsa pipewire-pulse pipewire-jack gst-plugin-pipewire and pamac install manjaro-pulse.
For whatever reason it doesn’t seem to have the original issue any more. Had to manually install kmix to get the media key control and visual feedback back, and the ‘audio’ submenu in the settings manager is gone, but I can live with that.