pressing and holding a key doesn't makes the action happens repeatedly

[Iago Barbosa]

I am having a problem with holding any key to do something repeatedly.

Example: You are writing something and you want to erase, so you click and hold the backspace to erase the letters.

In lubuntu 16 and 17 (the ones that i tried), both are having this bug, i click and hold the key, but suddendly it stops the action and i have to click several times to do what i want rather than just click and hold the key.