When I clone an issue which has attachments and thumbnails of those attachments, and I select the "Clone attachments" checkbox, the cloned issue correctly has the previous attachment, but the thumbnail in the description fails to be cloned correctly. It shows a square that has the text "Failed to load" and a Retry link at the bottom of it.
When I clone an issue which has attachments (and thumbnails of those attachments in the description), the thumbnails should clone correctly.