Example you dont allow tagging networks from core to asset fields. If we create asset example LAN/VLAN and if we have 10VLANs on customers end. if i add firewall that has asset link field LAN. I can add only one LAN asset to it. You need to update your networks to support VLANs and add location field to it. And there should be option to see all networks from fields. Example under select list.