Hello,
that has to do with the cylinder below the turret. The clamping mechanism is not as simple as it seems. It is actually a timed actuation, and if it is too fast or too slow, the clamping balls do not fall into place in the groove in time, and get stuck, leading to loose clamping. What you have to do is take the cylinder off, take it apart completely and clean it, lightly clean off rust or surface imperfections. Buy new seals if you can and put it back together and hope for the best. This will fix the problem 99% of the time.

John