Booklet printing in wrong order

I work for a commercial print shop, and we print booklets all the time on our Xerox C75 digital press.  I have a 24-page booklet created in InDesign CC printing on 6 sheets of 11x17 paper, 2-sided, which we booklet-fold and saddle-stitch on the printer.  I'm using Mac OS X El Capitan 10.11.1.  My layout is 12- 11x17 pages, and I manually place the 8.5x11 pages into the spreads:

Document Page 1:  24/1

Document Page 2:  2/23

Document Page 3:  22/3

Document Page 4:  4/21

Document Page 5:  20/5

Document Page 6:  6/19

Document Page 7:  18/7

Document Page 8:  8/17

Document Page 9:  16/9

Document Page 10:  10/15

Document Page 11:  14/11

Document Page 12:  12/13

This is how I always layout a booklet.  But when I print this booklet two-sided and set it to booklet fold (outside) and staple center (saddle-stitch), the pages come out in the wrong order.

The booklet ends up in this order:

1, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, blank(23), blank(2), 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 24

Pages 22 and 23 are blank, so it's hard for me to tell which is which.  I think I have it correct above, but it could be 2, then 23.

The thing I don't understand is that the booklet is mostly printed in reverse order, but not completely.  The outside of the covers print where they belong, but the insides print in the middle of the booklet.  And every other page in the book prints in reverse order.

I've printed this booklet before with no troubles. All I did this time was open it and hit print.  I'm thinking there must be some little step I've forgotten, or some setting that got changed I overlooked, but I keep going over it and it never prints right.  I literally print booklets every week, so it seems odd I'd forget something, but I don't know what else it could be.

Thoughts on what I might have missed?