I've got a list that is using custom forms for new items and edit. Customization moved screen elements around, but the Attachments part of the forms is pretty much stock.
If I edit an item, and click "Attach File," the UI goes to the normal screen and appears to work, even returning to the edit item screen with the new attachment listed under attachments.
However, when I save the item and reopen it, the attachment is no longer there.
I've found plenty of references to older versions of Sharepoint having this issue with custom edit forms, but it was supposed to be fixed in 2008, and it appears the 2013 default forms already have the "workaround" for this included.
Where can I begin troubleshooting why the attachments won't save?
FWIW, the list items that are imported via a C#/CSOM program have no problem having attachments attached to them with CSOM.