Graylab 300 Problem

I have a Graylab 300 timer. When I bought it off ebay two years ago the only problem was the lamp off occured about 1 second before the pointer reached zero. Over the last few years the error has crept up to 2 seconds.

Has anyone else had this problem. Before I drill out the rivets to open up the case and fix this, I just want to make sure there is not an easier fix.

Mine is fixed with a hex wrench. I don't know if they're all made that way but my hands are held with a small hex bolt.