Datastore isn't saving properly, can anyone help me understand & fix why?

I've tested this script in studios and it does the same thing in the actual game, It saves data and 50% of the time it doesn't. I'm relatively new to DataStore so I thought it was a good idea to ask you guys.

local DataStore = game:GetService("DataStoreService")
local ds = DataStore:GetDataStore("LeaderboardSaveSystem")
switch = false
switch2 = false

game.Players.PlayerAdded:connect(function(player)
 local leader = Instance.new("Folder",player)
 leader.Name = "leaderstats"
 local Speed = Instance.new("NumberValue",leader)
 local Rebirth = Instance.new("NumberValue",leader)
 Speed.Name = "Speed"
 Rebirth.Name = "Rebirth"
 Speed.Value = ds:GetAsync(player.UserId) 
 Speed.Value = ds:GetAsync(player.UserId) 
 ds:SetAsync(player.UserId, Speed.Value)
 ds:SetAsync(player.UserId, Rebirth.Value)
 Speed.Changed:connect(function()
	if switch == false then
	 switch = true
	 print("sanic")
	 ds:SetAsync(player.UserId, Speed.Value)
	 wait(7)
	 switch = false
end
	 end)
 Rebirth.Changed:connect(function()
	if switch2 == false then
    switch2 = true
	print("rebirth'd")
    ds:SetAsync(player.UserId, Rebirth.Value)
	wait(7)
	switch2 = false
end
 end)
end)


game.Players.PlayerRemoving:connect(function(player)
 print("player left")
 ds:SetAsync(player.UserId, player.leaderstats.Speed.Value)
 ds:SetAsync(player.UserId, player.leaderstats.Rebirth.Value)
end)