The valve area can be challenging. You may not be aware of it but this part of the nose moves when you breathe. Take a big breath in and notice the sides of the nose come in and out. Therefore grafts may shift or not receive enough blood supply, or become infected.
I would discuss your concerns with your doctor. If they do not seem to have any more options for you, look for another rhinoplasty or ENT surgeon in your area.

Brian Maloney