Bug where i and my friend are getting kicked from each other

Me and my friend are playing on ps 5 and he has the problem whenever i join him after 10 to 20 min he cant see me anymore and i cant destroy fnix bases cant loot anyting and he stands still and gets a massage which says the session is not available for multyplayer and when he joins me after the same amount of time he gets kicked from my session. He has nat type 2 so have i and he has restartet his router and even reinstalled the game but nothing worked to fix this problem we where 2 players in the sessions but also 3 or 4 sometimes