Ps5 Splitscreen not working

Sometimes the second Player cant join the session and the problem can't be resolved for days. When start is pressed on the second controller the game just prompts you to press start again. We have been playing on this World for about 40 Hours and had this bug happen before. We were able to resolve it by logging the second account off of PSN and back on again afterwards. Furthermore the shop cannot be accessed (Error Code D-0020) the dressing room of either of us does not load and whenever I quit the game it's stuck on “saving world” forever forcing me to close the application to quit the game. I suspect that all these problems share the same origin that's why I mentioned all of them. We also restarted the console countless times, deleted the console cache, deleted the in-game shop cache via the settings, reset the internet router, tried both wired and wireless internet connection, deleted and reinstalled the whole game, signed in and out of our Microsoft and PSN accounts respectively and it all didn't help. We are also running the newest Version of the game.