This question is a follow up to my original question, I've done a bit more reseach, i narrowed a problem down quite a bit.
I've also uploaded a sample .rdl to illustrate the problem
I've got the following report setup: a header (image in the body), two textboxes, and a footer.
First textbox has a little bit of text, and second textbox has lots of text. Second textbox can fit on one page by itself, but won't fit on the page with my header and the first textbox.
The problem is that for some reason, the second textbox in the report is unaware of other contents of that same report, and as long as that one textbox fits on one page - it will be moved to the second page. (once the textbox grows larger than 1 page - it will split, and will achieve the desired behavior)