If you cannot click the button:
- we’re in the Game Only input mode
- the widget (or its parent) is set to be not hit-testable
- the widget is disabled
- another widget consumes input
UI goes first in Game and UI mode; if unhandled, it tunnels to the PC. You cannot un-handle a button unless you actually use a precise-click. And even then, it’d be a hassle. I stopped using buttons for that reason alone - you just cannot shake them off.
Consider having a look at the widget reflector - it is a tool designed to handle this.
Start picking widgets in PIE, see what you get:
You could also Flush input on the nodes you have up there, in case something does get stuck, indeed.