"BuyETC is not a valid member of Frame"??

I have made a Shop GUI, and I have encountered an error. It is very strange. The Speed Coil button throws an error, but the RPG one works just fine. The error comes as, "BuyETC is not a valid member of Frame". It IS a valid member of the frame. As I said, the other one works just fine. The code for the coil is:

local img = "rbxassetid://99170415"
local selection = script.Parent.Parent.BuyETC.Selection
local price = script.Parent.Parent.BuyETC.Price

script.Parent.MouseButton1Click:connect(function()
    selection.Image = img
    price.Text = "Price: 1000"
end)

And the code for the RPG (The one that works fine) is:

local img = "rbxassetid://1960322961"
local selection = script.Parent.Parent.BuyETC.Selection
local price = script.Parent.Parent.BuyETC.Price

script.Parent.MouseButton1Click:connect(function()
    selection.Image = img
    price.Text = "Price: 5000"
end)

Help would be appreciated.