Please do try these troubleshooting steps that may help in solving that problem with your keyboard.
- Start by uninstalling/reinstalling the keyboard driver.
- Go to Device Manager and uninstall the keyboard driver then reboot your laptop. It will reinstall the driver automatically.
- Do also install this ATK driver from Asus Support that may help. http/dlcdnet.asus.com/pub/ASUS/nb/Apps_for_Win8.1/ATKPackage/ATKPackage_Win81_64_VER100030.zip
- If all these will not work try an external keyboard and see if the same problem will persist because if it will not happen you'll need to do a complete factory reset.
- And if the factory reset will not work the only solution would be to replace the keyboard itself.