Have you lubricated the mechanism? Also have you checked to see that all the screws are tight? If you remove the screws that hold the lock together and take a look there are a couple flathead machine screws on the inside that can work loose in time and cause a problem. Just my experience and observation. I like the original Tri-Flow product for lock lubrication. Use the little plastic straw for accuracy of application. It is not advised to use loctite on plastic, last time I checked. Easy does it.
Strike while the iron is hot. Live every day as if it were your last and one day you will be right.