Why is detecting the spacebar being so laggy?

I am trying to make a script that allows the player to do a short hop by quickly releasing the spacebar after pressing it, or to do a full hop by holding it down. To track the spacebar I have a BoolValue called "space". However, this BoolValue is laggy and doesn't respond exactly as it should. This makes doing a full hop unpredictable and hard to do. I have another BoolValue for the w key which tracks the w key for something else, and it works perfectly fine. What's the problem here?

function onKeyDown(key)
    if key:byte() == 48 and running.Value == false and grounded.Value == true and script.KEYS.w.Value == true then
        running.Value = true
        pl.Character.Humanoid.WalkSpeed = runspeed.Value
    end
    if key == "w" then
        script.KEYS.w.Value = true
    end
    if script.debugs.Disabled == false then
    print(key:byte())
    end
    if key:byte() == 32 and grounded.Value == true and jumpsquat.Value == false then
        print("jump")
        jumpsquat.Value = true
        local jsquatanim = hu:LoadAnimation(jsquat.ANIM)
        jsquatanim:Play()
        wait(jsquat.Value/25)
        jsquatanim:Stop()
        -- jump
        if space == 1 then
            print("Full hop")
            local bp = Instance.new("BodyPosition", char.Torso)
            bp.position = bp.Parent.Position + Vector3.new(0,cst.jheight.Value,0)
            bp.maxForce = Vector3.new(0,math.huge,0)
            game:GetService("Debris"):AddItem(bp,.3)
        elseif space == 0 then
            print("Short hop")
            local bp = Instance.new("BodyPosition", char.Torso)
            bp.position = bp.Parent.Position + Vector3.new(0,cst.jheight.short.Value,0)
            bp.maxForce = Vector3.new(0,math.huge,0)
            game:GetService("Debris"):AddItem(bp,.3)
            end
        jumpsquat.Value = false
    end
    if key:byte() == 32 then
        script.KEYS.space.Value = true
        space = 1
    end
end

function onKeyUp(key)
    if key == "w" then
        script.KEYS.w.Value = false
    end
    if key:byte() == 32 then
        script.KEYS.space.Value = false
        space = 0
    end
end

    function onChanged6()
        game.Players.LocalPlayer.Character.Humanoid.Jump = false
    end
    game.Players.LocalPlayer.Character.Humanoid.Changed:connect(onChanged6)

function onChanged()
    if running.Value == true and script.KEYS.w.Value == false and grounded.Value == true and climbing.Value == false then
        running.Value = false
        pl.Character.Humanoid.WalkSpeed = walkspeed.Value
    end
end
function onChanged2()
    if running.Value == true --[[and script.KEYS.w.Value == false]] and grounded.Value == true and climbing.Value == false then
        running.Value = false
        pl.Character.Humanoid.WalkSpeed = walkspeed.Value
    end
end
function onChanged3()
    if running.Value == true and climbing.Value == true then
        running.Value = false
        pl.Character.Humanoid.WalkSpeed = walkspeed.Value
    end
end

mouse.KeyUp:connect(onKeyUp)
mouse.KeyDown:connect(onKeyDown)