I did not quite understand what you mean , sorry I 'm french I have not a very good level of English.
My workflow is:
An end user created a ticket . An agent assigns the ticket to the staff member.
The staff member concerned adds a custom form that I created before and in this form there is a field to send a file.Sending the file seems to work , but when I reassigns the ticket to another agent and he adds another custom form the file is not present .
I put an image attached to show you what type of field I set to send a file.