I was messing around a bit more with my broken pieces, using tape to test the adherence of the paint. It seems like the main failure point is anywhere there is two layers of paint on top of the primer. So on the lower torso (where the whole piece is silver and only the dark grey is painted on top), the grey can be pulled off of the silver. On the legs (where silver is painted on a base of dark grey), the silver can come off. Again this is deliberately attempting to pull paint off with tape or scraping. The paint adheres very well to the primer though, so any paint chipping won't be exposing metal, but the local base layer of paint, either dark grey or silver. I'm going to see if I can't find a match for the dark grey paint for future reference, I have a few spots to fix with silver as it is.
That's very surprising. Paint usually adheres well to paint I wonder if they used different types of paint???