I recently acquired a 519 in pristine condition and it and its case do not have any signs of use. All of the functions were working perfectly until I loaded it last night. I'm not certain what happened (I was following the instructions), but the rewind crank no longer had any resistance. It simply moves back and forth and does not seem to be connected to any kind of spring. It also seems to be loose, as if the screw holding it to the camera were loose. I hope that this is something that can be repaired at home by my son and I (if necessary we could ask one of my son's friends - a mechanical genius - to help). Does anyone have ideas, any help will be gratefully received. Thanks for taking the time to read this. Best regards, George