I have had my girls lock up before shed. It just looks like their tails are crossed a little too far "back" up to be a def lock. The vents are a little lower then where they are criss-crossed. Keep trying tho! And be sure to give that male a day or two off even if you haven't seen any locks. A quick meal will get his energy up to peak performance.

If you have any other males, something that has worked well for me is to put the two males together by themselves for ten or fifteen min's and then put your pastel in with her. You would be amazed how fast he will get it done. Good luck!