This happens when a page or attachment is added or deleted while there is an open editing session on a page that either links to the deleted/added page or uses the attachment.

Steps to reproduce

• Create a page and insert an image into it. Publish it.
• Click edit to start a new draft.
• Go to the attachments screen of the page and delete the attached image
• Go back to the page and press edit

Actual behaviour

• The editor still shows the attachment

Expected behaviour

• The editor should show "Unknown attachment"

This happens because the editor format of the page changes even though the page does not get edited. However, Synchrony still has the old editor format.

This is also true for links and macros. For example, deleting a page that was linked to from another page results in this same behavior, as well as deleting a plug-in while one of its macros is used on a page. The page in edit mode still looks like the macro is present even though in view mode it shows up as "Unknown macro."

Workaround

The workaround is to publish the page if this happens. Publishing the page forces Synchrony to get the new editor format. The editor format will now say correctly "Unknown attachment" or "Unknown macro" or will point to a non-existent link. The real solution in that case is to remove that part of the page or replace it with the new attachment or link.