I do not know if this is the same for the R line. But the M4-2 I had in the 'early times', with a motor, could not be fired without film (unloaded). The system that took up the exposed film was designed to slow down when the end of the roll came near. So, when the camera was fired empty, this system got out of order en then, when fired loaded, at the end of the roll the camera slowed down and stuck somewhere between frame 28 and 32. Repairing this was very costly.
But ofcorse this was a M camera and the first motorised 'standard' Leica RF.