Hello @chrisvdw @Katie_Clark,
Since images in surveys that reside in the Sent folder are stored in the My Survey Attachments folder, when a survey is copied to a new survey the images are not copied in order to ensure image files are preserved in the original survey and no name space issues occur in the My Survey Attachments folder.
The workflow noted above of browsing to the images and uploading them will ensure that the images are provided a new unique name and won't cause any namespace issues in the My Survey Attachments folder.
To edit answers within the repeat in the Inbox and Sent folder you will need to specify query allowUpdates=true in the bind::esri:parameters column of the XLSForm.
Thank you,
Zach