My friend showed me these 2 glitches that stop zombies from spawning in the finale. The only maps are the finales for Dark Carnival and Hard Rain.
Hao 2 get:
On Dark Carnival jump on the forklift's side until you can get on top of it. Then jump onto the pieces of wood below. Please remember to have all players on and kill bots.
On Hard Rain go inside the Burger Tank and stand on the table next to the coffee machine. Please remember to kill bots and get all survivours on.
Another thing is that Smokers and Jockeys can get you off of the places so get rid of them when youre getting ready.
When you leave the glitched area all of the Special Infected will spawn.