I don't believe your problem is with the "top screw". That screw is just a cap to cover the nut underneath that tightens the film advance lever. The "top screw" is also reverse threaded, so keep that in mind when trying to remove it. A friction driver will work to get that off. Then you will need some sort of spanner wrench to tighten the nut.
My ME Super had a similar shutter cocking issue. The film would advance, but it wouldn't always cock the shutter. Sometimes it would skip 3 or 4 frames before it would catch and fire. The problem with mine was one of the little rubber bumpers inside had turned to goo and was causing the mechanism not to catch right. I did fix it by tearing the camera down and removing the mirror box so I could access the parts that were causing the problem. Once accessed the fix was easy. Cleaned the goo off and put a very small drop of silicon lubricant on the pivot point and reassembled the camera. It's worked perfectly ever since. I suppose this fix will be intimidating for a lot of people, so be warned that it is not nessesarily easy.
Here is a picture with a green arrow pointed at the problem pivot on my camera.
A web site with lots of good info for fixing old cameras. Also has some links to the factory manual.
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