On/off conveyor

I like to make a conveyor which has to buttons: Basically one to turn the conveyor on and one to turn it off. I already made sort of a machine that could do this but the problem was, when there was a brick(not moving) on the conveyor while the velocity of the conveyor was 0(off state) and I tried to activate the conveyor again. The velocity did go up back again to 20 but the brick didn't move anymore.

Can someone explain me what I did wrong? This is my script

Parts = script.Parent
OnButton = Parts.OnButton
OffButton = Parts.OffButton
Conveyor = Parts.Conveyor

function OnButtonClick(playerWhoClicked)
OnButton.Transparency = 0
OffButton.Transparency = 0.5
Conveyor.Velocity = Vector3.new(20, 0, 0)
end

function OffButtonClick(playerWhoClicked)
OffButton.Transparency = 0
OnButton.Transparency = 0.5
Conveyor.Velocity = Vector3.new(0, 0, 0)
end

OnButton.ClickDetector.MouseClick:connect(OnButtonClick)
OffButton.ClickDetector.MouseClick:connect(OffButtonClick)

I am using 3 bricks the conveyor, onbutton and offbutton. The buttons have a clickdetector in them. Someone already told me it may be roblox's "sleeping parts".** The question is so, how can the conveyor itself make the brick moving again?(because I can step on it and the bricks will move again but I don't want that)**