Tween sending position crazily different from intended 4 studs up Y, how to fix?

Anyone know why when I tween a part to its own position plus 4 studs by Y, it completely sets it back to the origin?

local tween = tween:Create(part, tweenInfo, {Position = part.Position + Vector3.new(0, 4, 0)

Instead of going up 4 studs, it just completely changes position of all vector values, XYZ.