I think I may have also run into the same thing you are describing.
I had a set of styles setup as parent-child-grandchild. At one point, they all had three components, but at some point one of the components completely disappeared from the middle style (I think when I was deleting a Multiply Owned Handle, as stated in this thread).
It was a very annoying error, because I could not delete or change ANY of the three - C3D would crash every time I tried.
I finally fixed the problem by opening an empty drawing (not created from this template), and recreating the three styles in the new drawing, with the same names as before. Then I dragged-and-dropped them into my template, overwriting the "bad" styles, and it worked.
Sinc