When swinging and discriming out iron, if you go to dig a target and there is decayed rusted nail fragments in the hole, the pinpointer triggers on all the pieces. Even on little 2mm iron fragments, the pinpointer goes nuts (at least the Carrot on high sensitivity). It can be hard to find the actual target in scenarios like that.
Sometimes it helps to dig a little deeper and lay the dug dirt out and then pinpoint through the dug dirt. That way the target is out in the open and not "surrounded" anymore with the iron echoing off like in the hole.