I had a similar problem with my ME Super. I loosened the screws on the base plate (particularly the one below the shutter release) and something made a noise and everything was back to normal. It was probably just dirty and sticky and needed something to help loosen it. I have seen other posts saying that you only need to tap the base plate. It happened to me one other time, and I had to completely remove the base plate and poke around until it reset itself. Been going good for 10 years since then though