It contained some uploaded images.
After cutting and pasting the article into a new resource in Resource manager, the images did not show for some members on some browsers.
So where the images should have been was a "no image" error icon, even though the URL for these were to the correct URL in attachments. (And all attcahments showed fine in the ACP attachment browser.
So I had to re-upload the images into the new resource article and all is fine.
Is there a reason why images randomly don't show after cutting and pasting into the resource text editor?