He could be tired.
Or maybe he's become conceited and decided he is a stud muffin who gets all the ladies, and therefore can choose when he locks and when he doesn't lock.
In that case, I'd pair him with a male for a few minutes to put him in his place...XD XD XD or put him on "female probation".
Seriously though, probably female probation for a day...he might need a break.