Factory planet changes P4 output so when you change P3 from Data Chips to Planetary Vehicles both use SuperTensil Plastics.
Adding the second P2 item makes it appear that its working however its flawed as the factory doesn’t recognise the P3 been delivered. You have to delete the route and add it back in again.
Ideally should either accept the existing route or show an error that its not receiving the necessary P3 item.