While working on a Web Service operation to export quizzes & questions in various formats I noticed that the tag shuffleanswers is emitted twice at least for questions of type multiplechoice. Once with an integer value (0,1) and once with a boolean value (true, false).

<shuffleanswers>1</shuffleanswers>
<single>false</single>
<shuffleanswers>true</shuffleanswers>

This does not seems to bother Moodle's question import process but may be a problem for external systems.

Cheers.