But the answer is very simple, actually.
What happens is that it takes about 2 to 3 seconds for debian to respond to a press on the keyboard media keys (play, next, pause, etc).
And, to be frank, I have no idea why this happens, but the answer is here:
My purpose of sharing this is to help zorin, since I already have an account here 
If you guys do have contact with the Debian guys, maybe they would like to know about that too.
Cheers 