When you insert an image and then insert a character right behind that image (not on the next line!), the page is not saved correctly:
Instead of displaying the image and the text, the code necessary to generate that image is shown on the resulting page.

How to reproduce:

• create a new page
• add an image attachment to that page
• edit the page and insert the image
• click with the mouse behind that image. The cursor must be positioned behind the image, not on the next line. Now insert any character
  (see attachment)
• save the document
• the resulting page shows the code (Unable to render embedded object: File (image) not found.) instead of the image. See attachment