iPad iOS 9.3.1 and iPad Air: strange bug with keyboard

[Zombolo]

With passcode active the first keyboard click doesn't come up.
Even as I type this sentence, when I take 3 seconds break between sentences the first touch on my keypad does not register any sound.

Is it normal? Is there any solution for this?

Thanks in advance.

P.S. I already restored my iPad Air without any luck.

 

[Zombolo]

Anyone experiencing this problem?
It's an hardware related defect?