Why documentDownloadLink does not work in modification mode ?

Hi,

I have a process that displays a form. The latter contains an upload component and a donwload link.

The upload mecanism works fine as I can see the "document_id" saved in my rule Input.

Could you tell me why when the user is in modification mode of the form (not readonly) the click on the download link throws this error please?

    {"error":"APNX-1-0000-000","message":"Invalid Content ID","title":"An error has occured"}

If I save the form, leaving the process terminating, writing the data in DB, and then re-open the form (from the same process), the download button works fine.

When I am in modification of the form in the Designer, when testing the link, I can see the error is systematic, but if I launch a testing Expression rule to examine the document ID, I can verify that the document in file system Appian is fine :

    todocument(51755) => gives me the correct document

Any idea ? maybe is it the normal way to work ?

Regards