According to the Problems and Remedial Solutions section of the manual: "Should film residue or dust collect at the contact point (for film detection) located on the pressure plate side of the film holder, the motor will continue to rotate idly after all remaining frames have been exposed. However, in approximately 30 seconds the motor will stop turning. When the motor stops and the ON-OFF operation of the main switch is repeated, the motor will again be activated in idle rotation; however, avoid doing this, since it may cause problems with the film winding mechanism. After switching off, remove the film holder and clean the contact point of the pressure plate."
So remove the film holder and make sure there is no dust in the film chamber or on the film holder. It sounds like the motor keeps going because the dust makes it appear there is still film to be rewound (the 2-4 seconds of winding after the last fame is rewinding of the film, not advancing of the film as I had said).
Hope this solves the problem.
The manual is available on Butkus' orphancameras.com site.
