Flannel is tough.. I have no problem with the thick men's flannel shirt material that I take old shirts. I wounder if because these have been laundered often.
I wonder if working with the baby flannel fabric is harder because of the thickness??
I do have a quilted, but one large piece, baby blanket that made it through two children.. used quilt binding on this over 30 years ago.
good luck.. flannel is hard to work with sometimes. :(