TeleportService is making separate servers for players?

For some reason, this script doesn't fill up my servers. Max server size is 18, and Preferred Player Count is 15.

Any idea what's wrong? Sometimes it let's like 3 people join the same server, other times it makes completely different ones for everyone.

local TeleportService = game:GetService("TeleportService")
local level1Id = 966545804
local level2Id = 857960791



local Button = script.Parent
function onClick()
 local player = game.Players.LocalPlayer
    if player then
    local frame = script.Parent.Parent.Parent.Loading
     frame:TweenPosition(UDim2.new(0.5, 0,0.5, 0), "Out", "Bounce", 1)
    frame.LocalScript.Disabled = false
    script.Parent.Parent.Visible = false
    wait(3)
        TeleportService:Teleport(level2Id, player)
end
end

Button.MouseButton1Click:connect(onClick)

Thanks for reading