Having trouble adjusting pinda probe height  

Having trouble adjusting pinda probe height

I've been using my MK3 for the first time in about 18 months. I ran the calibrations, including the XYZ as well as the first layer calibration, then printed a calibration file. Results showed the nozzle was way too high, so I gradually lowered it to get good shape to the printed filament.

This ended up with the Z setting at -1.000 mm. I read that the Z adjustment should be less than that, say between about -0.500 and -0.700. I therefore thought I'd lower the pinda probe somewhat.

It's been a long time since I built the kit so I don't remember the probe details all that well. However, I completely loosened the M3 screw on the side of the plastic clamp holding the probe. I then tried to gently bring it down. This is where I ran into trouble. Even by manually spreading apart the clamp with my fingernail, it seemed like the clamp was still holding onto the probe. If I tugged firmly, I could hear it skipping past threading on the side of the probe. I didn't want to pull too hard in case I might damage anything.

When all was said and done, the probe came down too far, so I had to move it back up. Though I tried for an intermediate position, when I ran the calibration again it was obvious it was even higher than when I started.

Is there a trick for smoothly moving the pinda probe to achieve a desired height?