@mwcorg_2342If I understand it correctly, somehow mail merge produces a document with a lot of sections in one single page (although it seems the document has just a lot of pages). Therefore, you can try to define the range as follows: s1, s3, s5-s12. Just put a 's' in front of each number in the range and it works.
I have no clue what the concept is behind these kind of sections, so it would be nice if someone can explain that :).