UI Buttons usually take 1 click to activate, but if you merge load the scene it takes 2 clicks.
Attached is a test scene to demonstrate. Load the scene and click the UIButton and it disappears as intended. Merge load the same scene and the first click doesn't register, it seems to select the button instead. It takes a 2nd click for it to register and disappear.
Attached is a test scene to demonstrate. Load the scene and click the UIButton and it disappears as intended. Merge load the same scene and the first click doesn't register, it seems to select the button instead. It takes a 2nd click for it to register and disappear.