This was an issue in previous Battlefield iterations going as far back as BF4 to my knowledge and it's still here. I have this issue with two computers attempting to play in the same party with UPnP enabled on our home router, same outcome with UPnP disabled. Setting static IPs also does not fix the issue.
The only solution I can think of would be to force a static set of ports to each computer but I have no idea how the game would react. Also, the set of ports used by the game has not been announced at this time.
Finally, I could pay for a VPN to mask one of our computers as originating somewhere else, but that just feels silly.
