I am resuming this thread after a nine-month hiatus.
The problem has been solved. It took several buffs to work out that the long vertical screw column (in red circle) that hosts a series of moving components was bent or became otherwise crooked. Probably due to dropping or some forced handling. Making the carriage advance impossible. The whole machine was taken apart, screw straightened then the machine reassembled. An important lesson I think for Corona 3 owners.  https://app.box.com/s/x3f49t1sal26kc5sl9modqhqz6ycgfqy