UI input / input mode

For the purpose of debugging, since that only fixed part of my problem…
Is there a way to know what consumed an input?

201940-capture.png

I have this. As simple as it gets. Press event doesn’t trigger most of the time. Sometimes it does, not it appears completely random.
So, something has to consume that input. but I have no idea what.
Whats even more weird is that clicking fast works, while clicking slowly, either by holding the button down for longer or by having a longer delay doesn’t.