Hi

I've bought a second-hand Lenovo ku-0225 from a retailer, who didn't care to clean it before selling it to me. I've taken all the keys off, washed them and dusted off the keyboard, but I still find that many of the keys are binding when pressed off-center, and I often miss keystrokes because of that.
I know a person who has this exact model of keyboard, and theirs don't bind, which leads me to believe that mine is binding because of the environment it was used in, as it was filthy when I received it.
I have a hard time seeing how I could clean the keyboard further. I even tried lubing the "keystems" (?), but that made the keyboard feel really mushy, so that's not an option.
Do any of you know of methods to reduce off-center binding on a rubber dome board?