Text occasionally isn't changing in correspondance to an IntValue?

I have a script that changes the text on a health bar to correspond with an HP value, most of the time it works fine but occasionally it bugs out and either doesn't change the text to the new value or changes the text to a value I changed it to previously. If I click onto the text label it updates or something and changes to the correct value. Is this just a visual bug in Studio or is there something wrong with my script?

hpv = script.Parent.Parent.Parent.Parent.Parent.Parent:WaitForChild('ZombieStats'):WaitForChild('HealthPoints')

hpv.Changed:Connect(function()
	if hpv.Value > 0 then
		script.Parent.Text = (hpv.Value..' HP')
	else
		hpv.Value = 0
		script.Parent.Text = ('0 HP')
	end
end)

Here is a better script that updates every time!

hpv = script.Parent.Parent.Parent.Parent.Parent.Parent:WaitForChild('ZombieStats'):WaitForChild('HealthPoints')

while wait() do -- Every few seconds, do
    if hpv.Value > 0 then
        script.Parent.Text = (hpv.Value..' HP')
    else
        hpv.Value = 0
        script.Parent.Text = ('0 HP')
    end
end