So if you go into globals and set a pedal to be locked to say Master volume, or Filter, use the pedal to drop the volume (in the case of it being set to master volume) to zero.
Then change it something else, back to expression or filter in the globals. There is no way to get sound back short of putting the setting back in globals or powering off and on the P12.
The master volume knob has no effect. The above is the same if you assign it to filter in globals. Change it and you have lost control over the filter from the knob.
Obviously it’s work aroundable, but I can’t inagine this is desired behaviour??