onEditEnd and onSubmit only firing from Return key

I have an InputField in my UI, but currently I can only submit its contents via the Return key. I tried mapping other buttons to the Submit action (e.g. the tab key on keyboard and the X button on my joystick), but neither worked. I tested both onEndEdit and onSubmit (via the Event Trigger component).

That said, onClick is being called correctly when I remap my Submit button. I can navigate the menu with my joystick and alternate keyboard controls, but I can't submit the InputField without pressing Return. Why is this?