Incase of multiple attachment controls on Nintex form.
Submitter section – Attachment control 1 – Set as Default Attachment
Approver 1 section - Attachment control 2
Approver 2 section - Attachment control 3
Approver 3 section - Attachment control 4
Submitter uploads attachment and submits form.
Approvers open the form one by one , attach separate files to individual attachment controls and submit.
Submitter open the form again and sees all the approver attachments are added to Attachment control 1
For some approvers - attached files are missing in the attachment controls. For some no attachment. For some all attachments available.