How to completely disable keypress response in Ubuntu?

Question

Keyboard

Good afternoon, ladies and gentlemen. Perhaps someone knows a way to actually disable the system reaction to a disabled key through xmodmap ?
The bottom line is that the key 5 , located on a separate num-pad , often began to stick on the laptop . Moreover, it works arbitrarily, when it pleases.
Tried to disable via xmodmap in 2 ways:

xmodmap -e 'keycode 84='
xmodmap -e 'keycode 84=NoSymbol'

Keycode 84 just corresponds to 5 on the num pad .

keycode  84 = KP_Begin KP_5 KP_Begin KP_5 KP_Begin KP_5

In a regular terminal, notepad, default browser, the blocking works as it should - the button does not work.
But as soon as I run other programs that are not default from the box for ubuntu, the following happens:
1) Google Chrome - '5' will miraculously appear again if desired in the address bar, etc.
2) When connecting via SSH - ' ^@ ' will appear when entering the password.
3) When programs are conditionally launched into the background (I mean the launch of the python djangi project) - the terminal puts the symbol ' ^@ '
During normal scrolling of the terminal, it always resets the input cursor to the current position, as if I were trying to type something (+ the mouse cursor disappears, and the text input cursor stops signaling the readiness to enter a command).