It may be that the Keep Options (a paragraph attribute) applied to the text on the second page force a number of lines together that will not fit in the space available in the first page.
Nope, checked that...
Check the leading, space before, and keep attributes for the text at the top of the right-hand page, or the space after for the text on the left hand page. Also check the text frame options for the left hand page. There may be an inset for the bottom of the frame. You might also have a text wrap applied to an empty from or an object on a hidden layer.
Not sure I've time to loose with this kind of riddle! I've heads to cut soon!
If you really want help, send us your file! Thanks!