Take one look at the 4-player Deathmatch map, Payday, and you'll see why this map design is a problem. There's one way in and out of the player's base, and it's sealed by brimstone on the defender's side and obsidian on the attacker's side.
If the defender chooses to do nothing, the attacker can never breach their base and the match will never progress.
Obvious remedy would be "Don't play with shit people", but you could also just swap the obsidian to Brimstone.
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