If the nub was worn you could build it up a little with a small weld and then polish it down so it moves smoothly...
No welder? I can be pretty creative with a car battery and a piece of wire coat hanger
momentarily touching the grounded safety lever with the end of the coat hanger that is connected to the positive terminal to the nub spot would leave some of the coat hanger permanently attached to the lever...
but do that at your own risk. 
Be sure to wear safety glasses and close your eyes just as you touch the spot, because you will experience what is called a
BWF (BLINDING WHITE FLASH)
when it touches!