Every other mail merged booklet has its page order reversed when sent to Print Booklet

I am doing a 2000 address mail merge on an 8 page saddlestitched booklet in inDesign. There are no blank pages. The merge appears to be successful but when I attempt to use the "print as booklet" function, for some unknown reason it reverses the page order on every other booklet in the inDesign Print Booklet preview window. When I send the job to the printer, it prints every other booklet in the same reverse page order. Can you help figure out why this is happening?