It is a fairly easy repair. I have had this happen to several.
Drive out the metal pin at the connector end of the stick.
Use a wood block to tap off the sleeve(the 3-4 inch piece that acts as a stop at the connector end). It may take a little effort.
Remove the handle and slide the two section parts.
If you look at the section that rotates, inside the end opposite the handle you will find a slight ridge. The ridge is only about 6 inches long. This is the area that gets worn and causes the stick not to lock. Just take a little resin and paint in on top of the ridge. It does not take a lot. you may have to aplly and sand until you get it to the feel that you like.
The just put it back together. I replaced the metal pin with a small bolt and lock nut.