Attachments not showing in the Attachments Related List after merging
Attachments from an email message do not display in the “Attachments” related list after a successful merge.
Before the merge, you have a case with an email message containing and attached file that displays in the “Attachments” related list.
After the successful merge, the attached files from the child case no longer display in the “Attachments” related list but can be accessed from the cloned email message.
In the Winter 19 release, Salesforce introduced a new setting for Email-to-Case, "Save Email-to-Case attachments as Salesforce Files." Salesforce saves attached files in email messages as Files when enabled. Salesforce populates the "Has Attachment" field when processing email messages with an attached file through standard Email-to-Case. The “Has Attachment” field on the Email Message object shows either Attachments or Files to display in the "Attachments" related list on the case.
We believe this is a Salesforce Platform bug introduced with the "Save Email-to-Case Attachments as Salesforce Files" setting. The "Has Attachment" field is successfully populated on cloned Email Messages containing Attachments.