Found this with the latest OS release update. I did report it to Kemper support
PreConditions: Output Section Master is linked for all outputs but the direct out is grayed out or non selectable
Steps to Reproduce:
Start in Browse Mode and set the master to any volume.
Turn the Master to 0.0 and then switch to Performance Mode
At this point sometimes the volume locks at 0.0 and sometimes you can change the master volume but it does not respond immediately
This happens when going from Performance Mode to Browse Mode as well.
Work around:
Go into the Output Section and adjust the main out volume and then the master volume will respond again.
or
Reboot system
There might be other cases but I have been able to reproduce in the steps above