This is about a 4.1 LTS site that has been in intensive operation for a long time. Only recently, 4 weeks? ago, I upgraded it to 4.5 LTS. (Git upgrade, in situ). Except that almost all plug-ins needed to be upgraded too, all went fine.
Only now, trying to export question categories to Moodle XML and import to another course (on the same site) I noticed that the questions have multiplied. It looks like each question version has become a full question!
The annoying thing is that all these versions carry the version number 1, so I don't know which is the latest to delete the others. (Maybe there are dates in the original course, but I don't want to touch it, now I am in the second course.) Very tedious.
I took lot of precautions to keep the questions nicely in categories at course level, because in this course the quizzes and the question categories are one-to-one related.
If anybody wants to follow up, I can look more carefully. But absolutely no fun, I want to reuse those questions in a new course and move forward, and have little patience towards these non-ending changes.
Current Moodle is version 4.5.4. The previous one was 4.1.latest at that time, somewhere 15, I think.