Then you are not doing what I asked.  I can't see what you are doing now (what you claim moves the print to page 2) and I can only go off what you showed in your first screencast because that's all we have.  As I said in reply to your screencast, at the point just after you open your Pro-2100 job (and before you switch to print-to-file), turn off Freehand placement mode by clicking the hand button below the live view.  Then switch you print-to-file and specify your 18x24 page size and everything will work fine.  Unlocking that freehand mode from your Pro-2100 job before you do anything will correct the problem you caused by using a job that contains a freehand page where prints are locked to an absolute position.

Or, instead of opening a job designed for the Pro-2100, just set up your 18x24 print-to-file page first and simply add an 18x24 size print of the image you want and add the border/mat afterward.  Either way will work.

Mike