I have the most bizarre thing happening. I had a USB keyboard repeating keystrokes on a notebook with ubuntu 16.04.01 (but not the main one).
When I went to keyboard options to change stuff like key press repeat when held down. The USB keyboard would still repeat but the built in would not.
I tried to install Laptop mode tools to check if it was not some power configuration putting the USB keyboard on the blacklist but that did not work.
I upgraded to 16.04.02 and the problem was apparently solved. Now the problem came and went (weirdly after I installed steam but I don't think this is necessarily related).
It's a cheap plastic usb keyboard with no bells and whistles and the machine was a fresh formatted one.
Any idea of a general direction for me to follow?