I am on Mac Indesign CC. There seems to be a bug to do with master page spreads. I have an object on the RHS next to the gutter at 210mm on an A4 double page spread. However, when I apply the LHS master page say to page 2, the object on the RHS now appears on page 3, even though I do not have any master page applied to this page 3 yet?
It looks like this bug was fixed in CS3 but it seems to have reappeared in CS5 onwards. I found this previous thread about the problem in CS.
This is obviously quite a major issue as it means one cannot place items flush with the edge of the page near the spine! The only workaround is to move these items .0001mm away from the spine…which is not the best solution!