For those seeing this problem - do you use multiple albums and could photos from different albums be included for one person? If this is the case, perhaps the photos are being sorted by date, WITHIN each album; so if there are six photos from Album A, 2 from Album B and 1 from Album C the the result is A1, A2, A3, A4, A5, A6, B1, B2 and C1.
If anyone finds this to be the case (or otherwise) could they please reply to this message so that a solution can be ruled in or out.
Regards,
Ian Marr
Delia