This problem occurs because one of the boxes from the Master Page was modified on the layout page. When the page was moved, the Master Page on which that layout page was based was correctly reapplied to the layout page. Any 'Master Page-generated' object, such as a boxes or line, whose item level attributes (i.e., background, X/Y position, geometry, application of a frame, etc.) is altered on the layout page becomes a locally formatted layout page item. When the page is moved (causing QuarkXPress to re-apply the Master Page) or the Master Page is simply reapplied, then the now-altered object is layered to the front and the 'new' Master Page items are layered behind it.
Ensure that no Master Page generated items are moved/altered in any way while working on the layout page.