Sounds to me like the left side of your keyboard is malfunctioning. I don't know of a specific setting that will bring just your keyboard back to default factory settings. I would think you would have to bring the entire Chromebook back to factory settings.

My Chromebook wouldn't charge recently, and I had to do a hard reset, I think it was, using the refresh and power button. It worked.

But don't go by me. As you know, there are various things one can do such as powerwashing and other procedures, but I am not experienced in much of it as the hard reset I did recently was pretty much the only time I had to resort to any of those procedures.

In other words, I don't know the best procedure for your particular problem, I'm afraid.

You might find something useful here:

https://www.google.com/search?q=diagnosing+chromebook+keyboard+problems&rlz=1CAJCUZ_enUS853&oq=diagnosing+chromebook+keyboard+problems&aqs=chrome..69i57.12540j0j15&sourceid=chrome&ie=UTF-8