Q: keys "i" and "n" sometimes don't work during login

On two occasions at the login screen while attempting to resume my session, as I entered my password the letters "i" and "n" couldn't be used, they'd just sound an "invalid" tone upon pressing, I switched the input from my usual english qwerty setting to a dvorak keyboard yet the problem still persisted with the exact two letters despite the physical keys being different, even though all other keys were fine.

Restarting the system by holding the power button resolved the issue and allowed those two keys to work thus allowing me to enter my password and login, but... why is this happening? How can I prevent this situation?