Request items or Request Tasks do not contain the attachments added by the user when the request is submitted from the Service Portal.

If you check the logs you should see a SQL insert error because of duplicate unique ID sys_id on the RITM table. 

A business rule which is being triggered before Insert has "current.update()" or "current.insert()" in the script which causes the record to be inserted too early. Because of this, the code in the portal widget which copies over the attachment fails when it tries to insert the record that already exists. 

Remove the current.update() or current.insert() from that before business rule and it should resolve the issue.