Replace items error, index out of range

Hi, I am designing a roof and I want to be able to move the points individually but an error of ‘‘index out of range’’ keeps popping up. I checked the panel already and the index for as far as I know should be between 0-2 so I dont really understand what is going wrong. Could someone please help me? I have both the rhino file and the grasshopper file attached. For your interest this is my first Grasshopper assignment so I only understand the basics.
Parametric roof.gh (18.3 KB)
sculpture garden 2.3dm (3.9 MB)

Indices should be numbers

I don’t understand your objective? Looks like you are using Replace Items to replace points with vectors? When I disconnect Replace Items, the result looks reasonable?