C903 that happens alot when pepole use fingers , if you use a release a a string loop it usealy is not a problem . You might try useing diferant prongs , as I belive you are useing a GKF rest . They make an assortment of prongs and one with a slightly higher profile may prevent the problem you are haveing , of coarse that increases your chance of rest contact . If you are are useing feathers it woun't be a problem .