Could be a number of issues here.
The rod may be hanging up inside the tube, the spring may be bent, rusty, distorted or even broken.
There is (or supposed to be) a washer inside the tube that the spring rests on to keep it from falling down inside the tube.
The fork at the bottom of the tube that engages the ratchet may be distorted, bent or mangled preventing it from properly engaging the ratchet every time.
Suggest you dis-assemble the unit and inspect for damage and clean and lube while it is apart
Good luck!
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