Comment 23 for bug 1256511

this is another side effect of module-swith-on-port-available since iec958 does not support jack detection

you need to comment the loading of this module in default.pa

and

set iec958 as default sink

file bug report if pulseaudio cannot save the default-sink setting when you select iec958 as default sink

https://bugs.freedesktop.org/enter_bug.cgi?product=PulseAudio