I have been reading a little about these cranes and how they work.
The older ones just have a adjustable grip that is just a knob in the cabinet.
The operator would turn it up or down based on prizes to revenue ratio.
The new cranes are much more sophisticated. The coil in the griper is automatically electronically adjusting constantly. They may only have full power gripping every 10 or so plays. On some, the machine will lower the grip power after it raises the crane up. So it will pick it up, but when it starts to move the claw, the prize drops on the way to the win. It is a sneeky way to get you to put in more money as you think "I almost had it, one more try should do it."
I also read that a lot of states have laws that require a prize to be awarded on an average of so many plays. Around 10 to 15 depending on the state. But I am not sure how or who is testing the machines- maybe "The Crane Police"