Gerald gave you an excellent explanation. I'd suggest it's time to take or send that body in for a Cleaning Lube and Adjustment. Leica's factory service HQ is in Germany. There's a bunch of good info on how to access that service, paperwork requirements, etc., here
http://us.leica-camera.com/service/s...rters_germany/
although come to think of it, you may have a certified Leica repair specialist right in your own neighborhood. Silly me eh?
Mark