Drilling it is.

The thing is,sometime I have to do it when the pinball machine is on the trailer (in the street).

I have to get the headbox off becouse my trailer only fit 2 with headbox, but 4 without.

Another way if the machine has a normal pinball lock is to put a flat screwdriver in the lock and use a shifter to turn the screwdriver.
You may have to rotate it back and forwards to get it started.
The insides of the locks are only thin brass plates and they strip very easy.