I have a quiz uploaded to our MLE and one of the questions is a 'place items in correct order' question. If the user abandons the quiz at this question and the tries to reload the quiz tries to reload again at this question but displays message:
"CallMethod:q-099-test Display Question 'undefined' is null or not an object". I have tried deleting all attempts in the user history of the MLE but still it remembers!![:confused:]

Sounds more like something with that particular question in the published module than your MLE Sarah.
Sometimes just doing something dumb like moving the quiz bock on the page then putting it back fixes it.
Sometimes it doesn't though.
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Putting this in perspective you can spend a shed load of money on say one of the adobe suites and still get some very odd results. The errors are just more expensive to achieve LOL