C-s must be pressed twice I'm on macos Sierra (2013 Macbook Air). When I press C-s (control and the character s) nothing happens. Then, if I press it again (within a certain amount of time) it triggers. If I open the keyboard viewer in macos I can see that the s is not triggered until the second time it's pressed.

Any ideas on why it could be like this or how I can find out what is causing it?
I had khd installed which intercepted the C-s