Reply To: Master items reappear after inserting new page

This is not a bug or a flaw in the program. This is the way InDesign works. When a page changes from a left- to a right-hand page, the master page is reapplied. If you think about it, it makes sense and is the way it should work most of the time.

If you need to add or remove pages in a facing-pages document, then always add/remove an even number of pages each time.