So i made my custom capability and attach it to all players. I also made serialization and synchronization using my own packet (at least i think i do) to allow client (player) always access updated capability data after some changes. In my capability event handler class i've subscribed to PlayerLoggedInEvent and send updated data through my packet. The problem is the data just doesn't save after player leaves the world and sets to default values after player joins the world again. Any ideas how to fix that?