Ice skates edges dont grip?

Over the past month or so i have gradually begun to slide more and more when doing an outside edge on my right foot, i had my skates sharpened and this only helped a bit, the other edges now grip fantastically but the right outside edge doesnt. I go onto it and it grips then as i increase the speed i turn at it just slides sideways across the ice, i cant replace the blades because they are riveted into the boot, Does anyone know what is wrong and how i could fix it, or do i need to buy a new set of skates?