Sorry to dump this on you Sam, but I don't have time to investigate it right now.
Steps to reproduce: (there may be something easier than this, but this is the specific problem I noted)
1. Create a quiz with adaptive mode = yes.
2. Add a multiple choice question with several choices.
3. preview the quiz, and select and submit several different answers to the question.
4. Finally, click End test..., then submit all and finish.
5. Look at the history table under the question, as it appears on the review page.
6. Click the link of a previous state number. This will open in a pop-up window.
It just shows you the final state again.
It should show you the previous state.
Look closely at the URL. You will see we have an escaping problem. It will look something like
but it should be
Actually, very weird the way it escaped some = and &, but not all.