How do I get my code to not stop after this one part?

local s = script.Stat
local vals = game.ReplicatedStorage.vals
t = 0
while true do
	local plrs = game.Players:GetChildren()
 	if #plrs > 0 then
	t = 15
	repeat
		t = t-1
		s.Value = "Intermission.. "..t
		wait(1)
	until t == 0
	s.Value = "Get Ready to Wipeout!"
	wait(2)
	local mapselect = game.ReplicatedStorage.Games:GetChildren()
	local choose = math.random(1,#mapselect)
	curnum = 0
	for i =1,#mapselect do
		curnum = curnum +1
		if curnum == choose then
			mapselect[i]:Clone().Parent = workspace
			curmap = mapselect[i].Name
			s.Value = "The next course is "..mapselect[i].Name
		end
	end
	wait(3)
	local plrs = game.Players:GetChildren()
	for i = 1,#plrs do
		local num = math.random(1,10)
		plrs[i].Character.Head.CFrame = CFrame.new(workspace.Teleports["Part"..num].Position)
		plrs[i].Character.Parent = workspace.Ingame
	end
	t = 0
	repeat
		t = t+1
		s.Value = t..
		wait(1)
	until t ==300 or vals.Winner.Value ~= "" or #ingame == 0
	if vals.Winner.Value ~= "" then
		s.Value = vals.Winner.Value.. " has won!"
		game.Players[vals.Winner.Value].leaderstats.Points.Value =game.Players[vals.Winner.Value].leaderstats.Points.Value +50
		game.Players[vals.Winner.Value].leaderstats.Wins.Value = 	game.Players[vals.Winner.Value].leaderstats.Wins.Value +1
		vals.Winner.Value = ""
	else
		s.Value = "No one has won!"
	end
	wait(3)
	local ingame = workspace.Ingame:GetChildren()
	for i =1,#ingame do
		local plr = game.Players:GetPlayerFromCharacter(ingame[i])
		plr:LoadCharacter()
		
	end
	workspace[curmap]:Destroy()
	else
		s.Value = "Waiting for Players..."
		wait(1)
		end
end

Okay, so I looked up coding tutorials and I tried coding a minigame place. However when it gets to this part, it always freezes the timer and the code stops. I don't really understand why though.

repeat t = t+1 s.Value = t.. wait(1)

you cant put 2 dots after a value since 2 dots means followed by, it puts in the value for t but then it wants more due to those dots so if you want to have 2 dots in your value then you need to do the following s.Value == t..".."

I would use a while loop for this occasion. I developed a similar place, in which players would participate in various minigames, with a timer counting down each one. I used a while loop for that. Here's your code, for the timer, with a while loop instead.

local plrs = game.Players:GetChildren()
    if #plrs > 0 then
    t = 15
    while t ~= -1 do
        t = t-1
        s.Value = "Intermission.. "..t
        wait(1)
    end

Try that, and I hope it helps!