One of our content editors pasted text into an FCK Editor field from another source. Among the content was a backspace character (ASCII 8, or CTRL-H).

While Magnolia could save and edit this page without difficulty, Jackrabbit was unable to render that into XML, which broke publishing, backups, export, etc. for that page. We were eventually able to fix the problem by using the JCR browser to copy the data into a text editor, have it zap the non-displayable characters, and then paste the result back into the repository.

To solve this issue, I'd suggest that stripping non-printable characters from String values (or at least for the FCK Editor controls) before persisting them to the repository might be a good approach.