Did they say exactly what was wrong with your binding?
I had this happen to me about 12 years ago...my binding was
too flat. I found they want 'fat' bindings...full of fabric
or batting inside the binding. I had been trimming off excess batting before I machine stitched the binding on top.. Now, I sew the binding on by machine...then trim but
leave a 1/4 to 1/2 inch batting there to stay inside the
binding. The variance comes from how thick my batting is.
I do like it a little bit better with the full binding,
but I didn't realize until then that anybody cared.