I made a terrain generator but for some reason there are random holes in the map sometimes?

I have a terrain generator, and it generates terrain forever. But when it continues to generate terrain for some reason there are random holes in the map, why does it do this?

Here is the code:

local Part = game.ServerStorage:WaitForChild("GrassBlox") --For cloning
Part.Anchored = true
Part.FormFactor = "Custom"
Part.Size = Vector3.new(1, 2, 1)
local seed = math.random(1, 10e6)
local frequency = 2
local power = 10
local resolution = 100
local Iteration = 0

function GenMap(Offset1, Offset2)
for x = 1, resolution do
    wait()
    for z = 1, resolution do
        local y1 = math.noise(
            (x*frequency)/resolution,
            (z*frequency)/resolution,
            seed
        )

        local y2 = math.noise(
            (x*frequency*.125)/resolution,
            (z*frequency*.125)/resolution,
            seed
        )

        local y3 = math.noise(
            (x*frequency*4)/resolution,
            (z*frequency*4)/resolution,
            seed
        )

        local y = (y1*y2*power*power)+y3

        local Part = Part:Clone()
        Part.Parent = game.Workspace
        Part.CFrame = CFrame.new(x + Offset1, math.floor(y + 0.5), z + Offset2)

        end
    end
end

while true do
    if not frequency == 2 and not frequency == 0 then
    frequency = math.random(frequency - 1, frequency + 1)
    elseif frequency == 0 then
    frequency = frequency + 1
    elseif frequency == 2 then
        frequency = frequency - 1
    end

    if not power == 2 and not power == 10 then
    power = math.random(power - 1, power + 1)
    elseif power == 2 then
    power = power + 1
    elseif power == 10 then
        power = power - 1
    end

    Iteration = Iteration + resolution
    GenMap(Iteration, 0)
    seed = math.random(seed - 1, seed + 1)
    wait(10)
end