[CRITICAL] Can not join game with someone from same house.

My partner and I both play on our separate PCs, both of which are plugged into the router directly via ethernet cables.

We had similar issues on Apex Legends, Call of Duty Modern Warfare 2019, Monster Hunter Wilds and others. these are games known to have issues with multiple connections to the same game session. but were recently resolved by changing the below settings and working with our ISP.

We had recently managed to resolve this issue by enabling UPnP, static IP, Open Nat, Port Forwarding.
As of the latest update the issues are back and we can no longer join the same session without enabling a VPN. Some online state "double NAT" to be the cause of this, however double NAT is the standard internet design on Australia's NBN and restricting this could cause massive issues online. 

We have both been enjoying this game but this bug being back makes the game unplayable for us. 
Please resolve this as soon as possible. Most of our friends have either had to buy VPNs or just refund that game as it is no longer fit for purpose under Australian consumer law

Speaking with Networking engineers about the problem, and also a deep dive through these forums has given me some insight that it is often intentional or just an oversight in writing the Net code but this is a serious issue that has stopped myself and many others from being able to play EA and other companies games before and I would hate to be unable to play battlefield after waiting so long for a worthy successor to BF4.

We have also spoken with our ISP who have taken a number of steps to try to resolve this issue again but they eventually had to stop and accept that it is something that EA must fix on their end.

most recent error code was: 87003S:62001S:-8A
We have stable gigabit speed internet, a modern router, Cat6 cables, Fibre to the house, all router settings listed before are working exactly as intended and were checked on other games.

This issue was here at launch but we fixed it on our side, but now it has stopped working again after the update yesterday.