hey, if had to stick to what I know, I would be limited to reading only, zero posts !
(yeah, yeah, I know, but it's way too late for that now)
Mr Keenan is quite correct, of course, and his comment was not inappropriate
but I do own a SP101, and know it's different than a S&W or Security Six, and no, it doesn't just "unscrew" itself, never have seen an ejector rod "backed out" on one, never even heard of an SP or GP doing that, but if a revolver cylinder tried to "lock up" on me, any revolver, any design, I would clean/lube the gun and look at it anyway, along with looking for such things as crud under the star, because it's easy to look at, so I would do that before taking sideplates off and such... if it has a sideplate to take off
old habits don't always yield results, but they are free, no postage required
me, if I cannot identify the problem without stripping down to the innards, I will send it to the folks who made it.. (unless I mebbe could talk a Fuff or Keenan or 1911 Tuner et. al. into a free inspection & fix)
if clean, lube, flush, airblast, and visual/feel inspection don't get it done, the factory will get it done better than me; I don't smith 'em, I just shoot 'em and enjoy 'em
"hell, it's getting to where I can't even stay on a horse"
be well, shoot well, and be safe
no offense taken, nor any intended