Inconsistancy/Mystery question

[Melanie Moore]

I'm working on my Book 1 Mysteries/Inconsistancies question, and that 
brought ME to a question.  If an inconsistancy is *between* two or 
more books, rather than *within* one book, where does it go.

For example, what about the Hagrid-returning-Sirius'-motorcycle 
question?  It was SS/PS where he said he had to return it, but PoA 
where he said that Sirius told him he wouldn't need it anymore.  
There is no inconsistancy (on that subject, anyway) within either 
book, but there is between the two books.

Does this make sense?  Or maybe we can add some kind of Book-Spanning 
Mystery/Inconsistancy FAQ.

Melanie