Aren’t thr jaws bedded in an epoxy material ? If that epoxy starts to crumble it isn’t long before it is gone. I think the jaws have a keyed profile so that the epoxy is under compression also . Maybe whoever last replaced the jaws was short on the epoxy and thought “that’s good enough”. Unless the jaw or mantle (?) is cracked or broken that’s all I can help you with. I only helped a few times on the crusher and didn’t get taught much— only told “do this; don’t do that”