Okay, well... I've already handed the camera to a repair service. So far, without opening up the camera, they suspect the winding system will require a complete overhaul, quoted at $300 . They say that there is a possibility that more problems will be discovered once the camera is open, so I should be prepared for further costs if it turns out this is the case .
I asked about the film detection. They say that the film is detected by the roller, located just before the film goes to the pickup spool.
But they believe it is not a case of the camera failing to detect the film but rather the camera failing to detect that the film has reached the next frame when being wound - which apparently has to do with the winding mechanism.
I'll post back when I have more details. Thanks.