Lens not retracting when you turn off the camera

I had this problem for a while and after sending it into the shop I was told that it was because of a small piece of sand that had been lodged between the lens and the camera... So I was told that it is a good idea to wipe down the entire lens mechanism after each use where it might get dusty or sandy. I'm sorry this doesn't fix the problem if you are already experiencing it but you can prevent it! If you do find that the lens isn't retracting try turning the camera back on and off if that doesn't work I recommend service...