KC868-H8B input minimum time to activate

[Suhl79]

I've been playing with H8B device today and connected a momentary switch to it's input port. I also use MQTT Mosquito to publish/subscribe for the events. Quite often I didn't get the button press reported as apparently they were too short. I have noticed that I have to press and hold the button for around 0.5 sec to get it reported. Is it an expected behavior? I'm planning to use some inputs for the door bell application and short button presses are normal. It almost look like some kind of a button debounce technique was applied for the input signal, but it affected how short signals are being recognized. Please advise.