InDesign Data Merge Export to PDF Error - Blank Pages at end of document

Hi everyone,

We are using InDesign and the Data Merge feature to import names for certificates from Excel document.

All works well, only having 2 fields to import (First Name and Last Name).

All of the names are great, but it adds extra template pages but with blank fields where the data merge input is at the end of the document.

This is when you flick through the preview in InDesign and when exported to PDF.

There are no extra blank columns or rows or blank fields in any of the imported data.

And all of the names are importing correctly, so the blank fields are extra certificates, not instead of names that aren't working.
Any help would be greatly appreciated, thank you!

Jaime