Buttons not working when timescale is 0.

In my start function, I set timescale to 0, then I set one of my menus as active and it works just fine, including all the buttons. However, when I later call the same start function from another script, after it appears I am unable to use any of the buttons. Yet, one of my other GUIs that is activated in the same conditions but from its own script, also works fine.