Hi @jonas thank you for the answer.
I don't know if that was reason for the issue but after a Kernel update to Linux 5.14.2-arch1-2 and installing qt-gstreamer-1.2.0-4 clementine/strawberry are working as expected.

I'm experiencing a similar problem as in Strawberry starts muted in Pulseaudio.

First Strawberry always starts muted and if I manually unmute it in pavucontrol it gets muted again as soon as the track changes. So Strawberry is almost useless to me.

I did some testing and it seems only audio player are affected by this.
I see the same behavior using clementine and rhythmbox but firefox and steam games are unaffected.

Please help me to debug.