I was able to solve this problem.
If there are mappers in the future having this same issue, here's what I did.
I'm thinking that TW made the Zeds teleport to the closest possible spawn location to the player. I can't have that in my map since the whole premise of the map is to defend myself from the Zeds coming into my "building", can't have them spawning in the building itself.
The solution was pretty simple, I made the spawns far away enough from the building that the Zeds don't see a reason to teleport back.
I'm not sure of the teleport mechanics but I'm gonna guess that Zeds will teleport if they are some UU distance away from the player and look for the closest spawn location. If all the spawns are far away, they won't be teleporting anymore.
If you want to take a look at the example, I've uploaded my map in the beta section. Name is KF-Defence_Thyself. Its a throw back to the old defense map from KF1.