Dave:

I forgot to mention in my original post that the engine has shoes instead of rollers.  Actually the engine I have is a 1946 model with cast aluminum drivers.  It appears to have very little clrearance between the underframe and the center rail in comparison to my other engines, all of which have rollers.  I think the shoes are hanging up somewher on the uncoupling track.  I going to continue to poke around.  I would appreciate any further thoughts you may have.

Thanks!

Dave