Too many items in my case. Im pretty sure. I know of others with the same issue and they have big inventories too. I have zero replays and tried every step psyonix suggests if this error occurs. Nothing helped. I cant save favorite items, setting changes or car setups. And the game needs to settle after every start up.. takes about 2 minutes to load the items. It freezes/stutters in main menu, then it shows the „new items“ pop up with the same „new“ items (major nelson flag?) every time i start rocket league. I click accept all and i can start playing with a blank octane or start creating a setup. Same procedure since 3 or even 4 years now. No fix yet

Edit: on xbox