Yes exporting to PDF/X-1a not distilling.
Sorted, but very odd.
Document is facing pages with 3 double-page master spreads.
First 5 pages were set up to use masters 1A, 2C, 3A, 4A, 5A
I can export pages 2-5 and everything is fine. If I export pages 1-5, page 5 is misaligned again.
There is no content which crosses the gutters.
Page 2, although using master C had the master contens covered completely. So, technically it didn't matter what master page was assigned to page 2. So I changed the masters to A, A, A, A, A and everything exports as expected.
While this solved the issue, it doesn't make sence. There are other spreads in the piece which use a C master on the right and an A master on the left and they export fine.
Guess I'll chaulk this up to a gremlin.