Oddness with continuos expression pedal in mute mode

I have a continuos expression pedal (casio sp34)

It works fine, as expected, until I put PTQ 8.0.5 into mute mode (clicking on the volume meter, with the L on the right)

Then every time I press the pedal it it spazzes out. When I turn off mute, it goes back to working as expected

Anyone else see this?

Not a deal breaker, but curious

Note, simply turning the volume to zero doesn't do this. I'd just like "mute" to be less surprising.