Master page effects don't render properly unless overridden.
I have a drop shadow on a Current Page Number marker on my Master page.
On the document pages, the marker renders the correct page number, but the drop shadow is always the character that's rendered on the Master page (In this case, a "B").
Only if I detach the item from the master page will it render properly.
Kurt Lichte commented
When I print the page with the elements still attached to the master, it renders fine. So it appears to be an on-screen only issue.