I have a lab environment that has a main office and branch office using Palo Alto NGFW as Internet facing devices. I have a pretend circuit between the two offices. My fake Internet/eBGP cloud is all VyOs to create longer/shorter paths to multiple destinations. When I advertise a subnet from one office, BGP works great. As soon as I advertise the same subnet from both offices, the new path remains, but the old neighbor association is dropped by VyOs. I then tried dual-homed on the same PA FW at the same site. Again, the older path/neighbor was dropped. Palo Alto continued to attempt to attach to Vyos on the dropped neighbor, VyOs continued to receive the Hellos (seen via debug), but would never establish. As soon as the second path is removed from the Palo Alto side, VyOs then acknowledges the first neighbor and the old association and path is restored. Neighbors should remain associated and both paths should be seen in routing table, but path with best metrics should be used.
I saw this a month or two back, and I see now you have version 1.2, but I didn’t have time to check on 1.2, and if the bug wasn’t reported previously, which I don’t see it, it should still exist in 1.2.