Provide screenshots. People don't always have time to download files and open them. That aside it simply sounds like you scaled your shape layer instead of creating the path at the correct size. The copy & paste method uses the coordinates relative to the layer and those don't change when you scale a layer. Make sure to create your paths at their actual intended size or scale them by actually transforming the path and anchor points, not the whole shape layer or shape group.
As Melenium Says, it's a scale issue, your "C" shape should be at 100% size to be able to copy the path and past it without any trouble, check this quick tutorial to see how to fix that, https://youtu.be/nxlZFSon7iw