Sliding has no effect for items in the header and the footer. It would appear that there is at least a few pixels of empty space between the bottom of the last sliding layout object in the body and the start of the footer. If the size of the sliding objects works out just wrong, there need be just one such extra pixel of "white space" extending past the page break to trigger a next page--which will appear blank in your output.
If you pull the footer/body boundary up as tight to the lowest sliding layout object, you shouldn't get such an extra page.
Key facts about sliding layout objects:
- It's only visible in preview mode and when you print/save as PDF...
- Sliding fields will shrink but not expand.
- All layout objects below and in the same layout part as the slide/resize field need to also be set to slide up and resize.
- Objects in headers and footers will not slide.
- Portals will shrink/slide to fit the number of rows of records, but fields within the portal row will not shrink/slide.
- Fields will slide up only if Top alignment is specified for it and will slide left only if Left alignment is specified.
- Consistent side borders are difficult to achieve with sliding fields.
- In FMP13, hidden objects (”Hide object when”) will slide/resize.