The report writer is black art, no one knows for sure why things happen, BUT we have had this 100 page issue before...
If memory serves me correct I "think" it means your band/s height adds up to more than the height of a page, definitely need to be "neat" with your elements, and keep them very small.. making each tag smaller - as you have suggested - is a good start.
Plus, best trouble shooting is to cut the thing in half (eg copy your report and to keep it, then delete half the elements), and test, and keep going until you find the culprit.