Does the machine have to malfunction to have them open it, or do u just say you think you dumped something on accident and want to see if its in there?
I generally fill the bag so they have to open it to change the bag for me when I'm there. I've also use "hey, can someone open the machine for me? The bag in the machine is blocking the tube and I can't get my coins... I had the same problem last time blah blah."