I had similar problems (just with the numlock) when trying to use an older keyboard. I thought it may just be the keyboard, and with the relative inexpensive, new keyboards available, I bought a new one.

If it was working and then quit, and then works again, I'd think the problem might be that the older keyboard is worn out. There's a key matrix below the keyboard that may be not "connecting" with those certain keys and then at other times it is "connecting".

Dave

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