I tried so many got the same problems.
If me and my girl play bo4 i restart everthing.
Both ps4 has nat type 2 what is good.
But the first who start bo4 has open nat type in the game.
The 2e ps4 got moderate.
If the second ps4 restarted the game she get strict in bo4.
I read something about that COD has problems with 2 ip's ps4. are playing on the same network external ip going 2 signals out.
Sorry for my bad english