My left shift running animation works with the bar, but I am still having problems?

My Left Shift running works, but it makes the player keep running instead of stopping when they let the LShift button go. Can someone tell me what is wrong?

The localscript for the stamina and the stam bar:

local CAS = game:GetService("ContextActionService")
local RE = game:GetService("ReplicatedStorage"):WaitForChild("RE")
local fill = script.Parent:WaitForChild("top"):WaitForChild("fill")

local stam = 50
local speed = 16
local sprinting = false

local function sprint (str,state,object)
    if stam <1 then return end
    speed = state == Enum.UserInputState.Begin and 24 or 16
    sprinting = state == Enum.UserInputState.Begin
    while sprinting and stam > 0 and wait(.1) do
        stam = stam - 1
        fill:TweenSize(UDim2.new(stam/50, 0, 1, 0),"Out","Quint", .1, true)  
        RE:FireServer('sprint', (speed))
    end
    sprinting = false
    speed = 16
    RE:FireServer('sprint', (speed))
    wait(1)
    while not sprinting and stam < 50 and wait (.5) do
        stam = stam+0.5
        fill:TweenSize(UDim2.new(stam/50, 0, 1, 0), "Out", "Quint", .1, true)
    end
end

CAS:BindAction("sprint", sprint, true, Enum.KeyCode.LeftShift)

script inside of serverscriptservice:

local RE = game:GetService("ReplicatedStorage"):WaitForChild("RE")
local stam = game.StarterGui.ScreenGui.stam

RE.OnServerEvent:connect(function(player, request, data)
    if request == 'sprint' then
        player.Character.Humanoid.WalkSpeed = data[1]
    end
end)

PS: I have a RemoteEvent inside the ReplicatedStorage.