Never took the telescopic legs apart but most telescopic type devices use a caming action. They have a disk/cam that rotates off center which binds the leg in position. If it isn't working it is for one of two reasons. One the cam doesn't get a bite on the inside of the out tube, so it never fully cams to a point that it is totally locked. Or the cam is worn down and can't cam enough for a secure fit.
I have a an extension pool cleaning pole that works the same way. On mine the off enter disk has worn down so it could not get a good bite on the tube. I took it out and re bored it a little more off center that worked for a couple of years but eventually I had to replace the disk.
Simple process. Just turn a disk the inside diameter if the tube. Then drill a hole slightly off center and attach it to the lower part of the leg. Slide it in the tube and you are good to go.
Want more information on fix telescoping pole? Click the link below to contact us.