Can't be certain, but looking at the gif you provided I can see that the Z value is actually increasing as you move your cursor, even though the model of the ball is not moving.
Given that fact, I suspect a Constraint or Driver is present somewhere which is translating the Z coordinate into different, limited motion. As what you're moving looks to be an animation rig and they're often built with constraints and drivers in mind that also reinforces that guess from me - but without seeing the rest of the file or further details it remains a guess.
From the values in the gif, one of the balls is at around -4 Z, and the other only at -1 Z, and if they're actually constrained to stay within, say, 0 to 3 Z, this explains why they move differently. You can't see it, but one of them is already lower 'down' according to its own data.