Perhaps the white sauce didn't thicken because chef wrote step 11 twice but must have meant to add flour instead at step 12! Eh, chef/.
This is a wonderful recipe!! I made it with a friend (who is fantastically Italian) who called her Grandmother a few times for some help (We couldn't get the white sauce to thicken at first). This was the BEST lasagna I have ever had, EVER. Well worth the effort and time. I will be making this again, and again.