I can only think that there is something wrong in the publish method. I have published around 80 families to the CC for Structural and all work fine. But I have found that doing it with the iPart/table method (which is a bit more work) has more success than the easier, more straightforward method of creating the parameters, selecting the keys and then using the Structural Shape authoring method.
i have this same error, but im using a part from teh db and not one ive created myself.
the error is:
[WARNING] Frame Generator: Errors occurred during inserting Frame Member(s) [WARNING] Insertion of frame member(s) failed [ERROR] A frame member could not be created. The template file for ISO ISO 657/11-1980(E) - Hot rolled steel sloping flange channel sections could not be located in the Content Center library.