So at first I was getting an infinite loop error (when it just doesn’t start up the level) , so I checked out the console to look for easily solvable problems. In here, I noticed that my adblock was bugging out some things, so I disabled both Opera’s built-in adblock and my adblock+. Instead of just not loading the level, now it just crashes my browser :
Player session : https://gyazo.com/511ef6e29ddd4d4ff0c33f29075a5a9d
The level I was trying to access was “Dueling Grounds” (the pvp one for the second world).