Nikon S2 shutter problem

I have a Nikon S2 here, and the shutter speeds are all the same. I don't know what speed its running, other than pretty fas.t Changing the setting changes nothing. I'm a pretty good camera repairman but have no experience with these. Is this liable to be a tough situation to lick? Thank you.

I have zero S2 experience, but I plenty of Fs, which I think have some similarities at least in the shutter mechanism.

 

I know I've seen this on Fs when somehow or another they got "stuck" in rewind mode. Usually, exercizing the collar a bit and making sure it was firmly slotted into the "A" position would get them working normally.

Thanks. Apparently that was a part of the problem because it's acting better now. I woukdn'tc all it dependable, but at least the problem has been proved. I'll deal with it and everything else once I open it up. I have other questions. I've notice that I see no evidence of parallax correction of the viewfinder as I focus. Is this true? And does it really matter, since most photography is done 5 feet and beyond? Secondly, this camera came with a Carl Zeiss Sonnar 50mm/2.0. Was there any modification to the camera to take this lens, and will this lens cooperate with the rangefinder throughout its range?