Attempt to index nil with visible

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#1

Ive just changed my normal gui frames to scrolling frames, the layout and order of these have stayed the same throughout the gui, however now im getting the following error:

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Even though from what I can see theirs no reason at all for this, this is the script:
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This is what it prints. clearly showing the correct name:
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This is how the gui is layed out (skinsframe is set as mainframe.skins):
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#2

:WaitForChild(), for UI elements, from that I mean something like:
local Mainframe = Player:WaitForChild("PlayerGui"):WaitForChild("MainGui"):WaitForChild("Mainframe")

#3

Nvm, stupid mistake, forgot to delete the previous skins frame you can see at the top under the core script. not sure how ive missed that