I suspect that there is a current limiter on each gear's circuit. That is what triggers the power off. If the worm is bent, dirty or dry, that could cause excessive current draw. But, … another issue could be a burr or dirty surface in the gear's pinion tracks and/or some of the jet guys have slightly rounded off the sharp point on the gear pinion track. If the "rounding" is done correctly, it does not affect the locking.