Just freezes and doesn't spawn the zombies, how do i fix it?

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Problem

Just freezes and doesn't spawn the zombies, how do i fix it?

Whats wrong

You're yielding the entire game when you make a while (condition) do end loop (assuming (condition) is a truthy statement)

In this case you're doing while math.random(1,3) do ... end with no sort of yield. math.random(...) returns a number and numbers have truthiness. Example,

if 1 then
    print"truthy"
end

This will output "truthy" when ran since 1 is a number and numbers have truthiness.

Solution

Yield your second while do loop to prevent it from hanging the game.

 --// *(assume condition's are true)*
--// this will hang your game

while (condition) do
    --//
end

--// this will not hang your game
while (condition) do
    --//

    wait()
end

Code to copy if you're lazy or confused

while wait(5) do
    if game.Lighting.ClockTime >= 18 or game.Lighting.ClockTime <= 7 then
        local zombies = game.ServerStorage.Zombies:GetChildren()
        while math.random(1,3) do
            for i = 1 , #zombies do
                if i == math.random(1,#zombies) then
                    local c = zombies[i]:Clone()
                    c.HumanoidRootPart.CFrame = CFrame.new(math.random(-50,50), 5 ,math.random(-50,50))
                end
            end
            wait() --// yields for 0.03 seconds to prevent game from hanging
        end
    end
end

Fixed, Needed To Rename The Zombies To A Number And Needed To Add A Wait Thanks