Zombie spawner doesn't work as intended, why?

Ok, so I've ran into a little bit of a problem, I'm making a zombie spawner script and the zombies do spawn, but instead of spawning in all the possible spawn locations (which are invisible Parts) they all spawn in the same one

This is the spawn function:

function Commands.SpawnZombie(amount, class, safeMode)
    local zombieType = game.ReplicatedStorage.Zombies[class]

    for i = 1, amount do 
        if safeMode == true then
            if game.ReplicatedStorage.ServerDetails.RoundActive == false then
                return
            end
        end

        local zombie = zombieType:Clone()
        zombie.Parent = game.Workspace.NPCs

        local RandomSpawnLocation = GetRandomSpawnLocation()

        zombie.PrimaryPart.CFrame = RandomSpawnLocation.CFrame
    end
end

And this is the GetRandomSpawnLocation() function:

function GetRandomSpawnLocation()
    local SpawnZones = game.Workspace.Map.SpawnZones:GetChildren()
    local randomSpawnZone = SpawnZones[math.random(1, #SpawnZones)]

    local SpawnLocations = randomSpawnZone:GetChildren()
    local RandomSpawnLocation = SpawnLocations[math.random(1, #SpawnLocations)]

    return RandomSpawnLocation
end

A bit of information: The GetRandomSpawnLocation basically gets a random SpawnZone (which is a big part with alot of small parts inside it) then it gets a random SpawnLocation which are one of the small parts, and returns that location

But as i said, even tho im firing the function every loop, it still spawns them in the same place. why does this happen? please help :c