Need some advice.
When working with, first it was pretty hard to turn the knob to open the back extension and finally the knob do not works anymore when trying to close the back extension (the knob comes out instead of moving the extension).

Middle and front extensions are moving well.
The front extension goes very easy, the middle one is a little less easier than the front one, but the back extension was always rough.
Can anyone tell me how to repair my Deardorff and obtain nice extension movements ?
Thanks a lot folks.