From a quick test, it looks like if you hover your mouse over the Fold button, and then try to use the Fold+Stack hotkey, it will instead press the Call button. This is because when you hover your mouse over the Fold button, the button changes color, and SaT then thinks its not visible, and thinks there is no Fold button at all, and instead thinks its trying to click 'Check'
Please test and confirm if this is when its happening for you
Please test and confirm if this is when its happening for you