Well it's not that its crashing, its that its disconnecting (two separate things, you'd have to test it online for everyone to disconnect)
Your going to want to increase the max stock if theres only 1 hero to chose from
and your going to want to remove the "This Map is fun" from the loading screen, it simply looks, how shall I put this, like your map really isn't that fun but you still want to get them to play it, the map should speak for itself