Why do my Unity Buttons need multiple taps to finally work?

As the title suggests, I have a screen with two canvases. Both literally a copy of eachother, but simply having a different layout for my Portrait and Landscape orientations. As and when the orientation changes, I disable to appropriate Gameobject containing the Canvas.

Now, I've never had any problems with the other buttons from the previous canvas open, but I've got this problem where my active canvas needs multiple taps on the same button to finally WORK.

Should I be doing something differrently?