Plutonium

Basically levels/classes don't save for me. I use the /unlockall command so unless I'm missing something after that or a command I need to put in so everything saves but my game keeps crashing and I'm tired of having to make new classes. And when I'm in a game everything will be working completely fine and then everything freezes for a minute and then the game disconnects and says "server overflow"? I have no idea what's the cause of that. It happens randomly too it seems.