In regard to your question about shutter timing inconsistencies being consistent, (whoa!!! that even twisted my brain into a pretzel for a bit!!!, I have heard others post that even with a CLA that when the shutter timing was adjusted it soon returned to it's predisposed timing. (Sounds like a female trait to me). I don't know that to be true, just what I have heard. So a number of photographers simply test their shutter speeds and then note the actual timing for consideration when exposing film.