id say the next step to try is the actual latch mechanism is probably stiff. i had a trans am that did this too. the cable broke and i had to repace it and the problem continued. so what i did was remove the latch and soak it in gasoline for about an hour. this loosens up old gunk built up over time. then spray it heavily with a can of brake cleaner. once its all dried off, grease the mechanism well and reinstall. when i did this, the hood POPPED up like ive never seen any chevrolet do, lol. hope this helps.