This has been fixed in InqScribe 2.0. Foot pedal shortcuts now ignore modifier keys by default.

What you're seeing is a bug/feature in InqScribe 1.5. The issue is that foot pedal shortcuts respect the modifier keys. So “center pedal” is not the same shortcut as “shift-center pedal.”

What is happening is that you're pressing the center pedal, so you're playing until “center pedal” is released. When you press the shift key, you essentially release “center pedal” and press “shift-center pedal”.

We're fixing this in the next release of InqScribe. There are some cases where it's nice to be able to use modifier keys with pedal buttons, but we're going to make sure that, by default, pedals ignore modifier keys.

In the meantime, you can work around the problem by defining “shift-center pedal” to play until released. Then, when you press shift, even though “center pedal” is released, “shift-center pedal” will kick in and keep playing.

Here are instructions for setting up the foot pedal in version 1.5.2.