After more investigation, I have found 23 examples in one database of e-mails with wrong attachments, which have occurred since upgrading them to Standard ERP (8.4) in October. Looking through RLinkVc and Attach2Vc, I can see that the incorrect PDF being attached has an earlier attach number than the correct PDF which is also attached. Sometimes it is the previous attachment in Attach2Vc, sometimes it is up to 30 attachments away. As of yet I have not found a connection between these - the companies and record types vary.