There's a glitch on the Xbox where if you set one of the layouts to alternate(where it switches melee and crouch/slide), the sniper zoom stays as the RS and so it causes you to crouch whenever you try to zoom and vice versa. IMO a better button for sniper zoom would be the LS because that doesn't restrict the button or stick layout, whichever it may be, and cause you to play on a layout that you are unfamiliar with. It could also just switch to whatever the melee button is, and therefore it would be the B button in the layout i've chosen, which is somewhat restrictive but a far better choice than the RS. And please don't make it so you just can't crouch while scoped to try and solve the problem because crouching is an important part of sniping.
EDIT: Also, while sniping, movement is usually not used very much whilst scoping, and so therefore the most logical choice would be LS. Just asking for a quick fix.