Sounds like you've set your merge fields to "slide up". Also select the "resize enclosing part" option for each such sliding object. And make sure that all objects on your layout alongside or below your sliding objects are also set to slide up and resize.
Key facts about sliding layout objects:
- It's only visible in preview mode and when you print/save as PDF...
- 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.
- Container fields will slide only if Top, Left alignment is specified for it in the data formatting section of the Inspector's data tab.
- Consistent side borders are difficult to achieve with sliding fields.
Resize Enclosing part did the trick.