Good afternoon and thank you for letting me be part of the community. 
I am building a form under a "Assign a Task" that is asking the user to modify an existing file that was already attached when the user created their initial list entry. The Workflow shares the same logic "Call HTTP Web Service" to initially grab the files from attachments and then move them to a folder. Later on it branches into an "Assign a Task" where it attempts to do the same thing but only keeps referencing the initial files and not the ones on the "Task" form attachments. Is there a different URL that I should be referencing with regards to "Task" form attachments verses other forms?

I.E.
‍{Workflow Context:Current site URL}‍_api/web/GetFileByServerRelativeUrl('‍{Variable:AttachmentURL}‍')/copyTo(strNewUrl='/sites/Sandbox/Shared Documents/Under Review/‍{Variable:AttachmentFileName}‍',boverwrite=true)