Following Chris's line of thought, I doubt the problem is with the
cylinder release bolt. Even if it were stuck forward, that would not
stop the cylinder from opening. The natural position for the bolt
with the cylinder open is forward, because of its rear-mounted pin
and spring pushing it forward.

It well could be that the extractor rod has come unscrewed slightly,
jaming it up against the extractor rod.

However, I think there is something else going on here. If the
center-pin return spring is working properly, even if the extractor rod
has come loose, the bolt (thumbpiece) would be returned to its
normal position. I can't tell, for sure, if the thumbpiece is jammed
all the way forward - it looks like it not quite all the way. It looks
more like the center pin is stuck in the extractor rod, either because
that assembly is bent, or something corrosive has gotten in there, and
is causing it to be stuck.

The first thing I would do is take the side-plate off, and see what
position the bolt is in. If its not all the way forward, I'd get a rod
up against the rear face of the front part of it, and tap it with a
hammer, to see if it will come loose.

A couple-day soak in Kroil may do the trick, as well.

Mike Priwer