I don’t believe there are any public facing tools to see carrier routing. Sure would be nice, if there are any please post them here! I have seen where a losing carrier does not tear down their translations which causes the situation you describe. Comcast was real bad about this a couple of years ago. Have you reported this issue to carrier 2? As the winning carrier in the number port, it is their responsibility to make sure the port is complete and to contact the losing carrier if necessary.