my Esssex J Bass buzzes on controllably. i've raised the action to what i'd call medium... i'd hate to have it any higher. but is this a problem with poorly cut nuts? i've heard bad things about SX nuts, and i'd like to know beforehand. some strings buzz even open. the problem is the worst at the 7th fret, on the G string mostly but it happens on the other 3 strings as well.