Update Document Metadata with SharePoint Connected System (Error: Server relative urls must start with SPWeb.ServerRelativeUrl)

Good morning, 

I can upload documents and list with the system logged in, but I am having trouble seeing if I can modify the metadata of a document, as I get the following error:

The construction of the request is done by Appian and I can't change the one it uses (Path) to the one it tells me (Url).

Does anyone know how I can do it or what I am doing wrong?

Thank you very much for your help