Typing on Mac: Keys Repeat or Additional Letters are Added

Hi there -

I've run into a new issue on my Macbook in that when I am typing, I will find keys will be repeated even though I do not press them, or the mac often appears to have a mind of its own and add into an additional string of letters.

I've turned off the repeat key slider in the system preferences but I still seem to run into this issue. Any thoughts would be most appreciated!