Why wont this work?

local MoveUntil = 20
local Text = game.Workspace.Text

while true do
    if game.Players.NumPlayers > 0 then
        Text.Value = "The game is ready"
        wait(2)
        Text.Value = "The battle will begin in: "
        for i = 10, 1, -1 do
            wait(1)
        end
        Text.Value = "All fighters to the doors"
        wait(2)
        Text.Value = "The doors are now opening"
        wait(1)
        Text.Value = ""

        repeat 
            for k, r in pairs(game.Workspace.InvisibleWalls:GetChildren()) do 
                r.CFrame = r.CFrame+ Vector3.new(0,1,0)
            end
            wait(0.1)
        until game.Workspace.InvisibleWalls:GetChildren()[1].Position.Y >= MoveUntil

    else
        Text.Value = "You need 2 players to begin"  
    end
    wait(1)
end

Game stops processing when I go into solo mode at 50%