I think the mistake is an internal face.

Much easy to help you if you post the model with the mistake to find it.



If it could help you I made in Moi a Subd with your first hand.
Moi is not the easiest tool for subd, but it's the only one I use now.
I takes much time but patience gives pretty good model.
As last one, you could improve it, because I'm not a specialist in subd.

Have fun...