ui buttons become unclickable

hello.
I have around 6 scenes in my project. each of them has several buttons to click.
whenever i build the app, the buttons in some scenes become unclickable. when i re build they become clickable and the buttons on the other scenes become unclickable. what could be the reason?

Check if there is only one “EventSystem” or not? if you have more than one “EventSystem” in your scene this can cause the issue, or if there is no “EventSystem” it can also cause this issue. Make it sure that you have only one “EventSystem” in your scene and that is always active