cos-ct-extends.1.4.3.2.2.1.b: The content type of a derived type and that of its base must both be mixed or both be element-only. Type 'aa....aa' is mixed, but its base type is not.

Both the content type of a derived type and the content type of its base must be mixed or must be element-only. The content type of type aa....aa is mixed, but the content type of its base is different.