When using Document Generation action in Nintex Workflow for Office 365, with the Table Data Repeated format, configued type as Row.
The template type .pptx will create a new table for each row in the corresponding workflow collection variable, instead of creating a new row in the same table.
This behaviour is a PowerPoint limitation in that if the template does not provide enough rows in the same table, it will create a new table.
The workaround of this behaviour is to create dynamic rows when using template type .pptx.
If the collection variable has 5 rows, then you will need to create 6 rows in the table, with the details below:
1st row: header
2nd row: table start tag and table column tag
3rd - 5th row: empty row
See Use Row as Repeated format type for the details.
This behaviour only occurs in a Powerpoint (.pptx) file and won't affect a Word (.docx) file