I admit to being guilty of learning the hard way many times, and this time I learned not to do derived configurations of the default configuration in complex work.
When I convert a plastic part into a cavity, the easy part is getting the whole part with shrink removed from a cavity block entirely encompassing the part.
I typically add an "Ejector Side" configuration & then derived-configurations for that which contain the outer cavity block, then inner sleeves and pins as I remove material. I do the same with the "Sprue Side" configuration.
The last time I did a pair of parts, one was done like above, but the other, I made a mistake. I started adding derived-configurations to the Default. This resulted in all sorts of errors that needed fixing when I changed the size of the cavity block. It is easy to "fix" the overall problem, but time consuming to wipe all the 6-9 derived-configurations and start it over.
I suppose if I read all the Help files, I would have found it earlier, but then again my head might have exploded, too.
Bo