As of the new MA plugin everything is going smooth, but in the new map there has been problems caused because of where it is positioned, PVP is on inside the lobby and the spectators box. this is inconvenient as when they die they go to the spectate arena and are not able to click the iron block to start the Mob Arena. After that you usually get pissed, knowing people around 10 and don't bother doing back to the arena to click the iron block, therefore everyone has to leave and come back.
Another downfall is when people go AFK inside the lobby without clicking the iron block, So, again people have to wait.