Toggle Buttons - Clicks and Keyboard Shortcuts Don't Mix?

Hello! I can't figure out how to work around an issue with toggles.

I followed the instructions at this post:
https://www.articulate.com/support/storyline-2/how-to-create-a-toggle-button

It works great for clicking the toggle button using a mouse, but trying to add a keyboard shortcut option in addition to the mouse-click is causing an issue.

The toggle button works as expected, but it only works consistently when the user clicks the button with a mouse. If the user starts a slide and uses the C keyboard shortcut instead (to toggle a captions layer on/off, in this case), the keyboard shortcut will continue to work ONLY until the toggle button is clicked with a mouse. Once the button has been clicked with a mouse, the keyboard shortcut no longer functions and the user MUST use the mouse from that point forward on the slide to trigger the toggle (unless the slide is replayed, in which case the scenario begins again).