I had a feeling that this might be the answer. Indeed, when I loaded the camera, I had to get some "slack" out. The camera's shutter release would not fire. I keep the MD-11 attached, and so I used the MD-11's shutter release in order to load the film.
Also, the MD-11's red "end of roll" light went on as soon as I shot the last frame (which should have been 36). I heard the shutter go off, but did not hear the motor wind (because the end had been reached). Whenever this happens, I always get a bit nervous, as I have seen frame 37 get smashed into the end of frame 36. Thus, I now will only go up to frame 36, and then stop. This is why I was surprised that I got the red light, as it usually does not go on at 36. It will go on at 37, but I now avoid trying to get 37, as I want to avoid the double exposure effect (error) with the end of 36 and the beginning of 37.