I propose the existence of a primitive system behind the transformation problem:



Fact: They're pony-like insects relying on a female compatible entity to keep the clan reproducing. They reproduce by the means of eggs.



The reproduction system has multiple flaws, 1 being the eggs: when Celestia used a magic buckshot attack on Chrysalis and her army in a comic (as I were told and linked), the attack didn't only inflict painful permanent physical damage, it consequently damaged the reproduction DNA in Chrysalis. The reproduction system re-reads the DNA every time Chrysalis enters reproduction, so the changes are instantly in effect between reproduction modes.



^ Consequently the Changelings may not look all the same, but to them the holes aren't just physical differences, they're a thing their brain (or, as I've created a concept of the magic abilities being a computerized system within the user's neural network and brain with a fair degree of built-in intelligence so the user doesn't need to bother with his magic's overall function) doesn't see as anything that matters in their transformation. (Hell, probly those holes don't even matter to their overall function although they can feel them when they touch them.)



^ Thus, there are 2 paths what happens:

1) pushing the process of transformation into another Changeling too far leads to total system crash for overloading the brain during processing too much identical transformation data; the transformation just won't know what to do with it even if the processing succeed.

2) they were in the final stage in the process of transformation, but the brain kept on getting fatal errors for too identical, senseless data, and eventually couldn't deal with them, leading to total system crash.



My concept in those paths doesn't have much of a factor since the magic systems were waiting for the brain to finish processing, but the user fainted (total system crash).