First check the keyboard settings if it's set to the correct Region and Language.
- Go to Control Panel and look for Region and Language.
- Make sure all tabs are set to United States.
- Try typing again but test it as well in Notepad.
- Lastly, uninstall/reinstall the keyboard driver
- Go to Device Manager then right click on the keyboard driver and select Uninstall.
- Reboot your laptop to and it would reinstall the keyboard driver automatically.
If all these doesn't work, you may think of replacing your keyboard already.
Thanks, it's still not working though. Is there any way to test if it's a hardware issue (like the laptop keyboard itself is broken)? It mysteriously happened overnight and randomly affects different spots. I can't help but feel like it's just a virus or I downloaded some weird update.