Users reported incorrect grades for quizzes being placed in gradebook. Examples included impossible results e.g 45 / 10.

Investigation revealed quiz regrading was examining all user quiz attempts in the moodle, not just for the selected quiz. The step to fetch all attempts for users does not always restrict to the regraded quiz; in our case this happened when picking a few attempts only (1) and regrading selected attempts.

This is fixed by adding an extra condition to the all user attemps query that restricts to the correct quiz, so attempt grading works from the correct attempts.

Unknown if this also affects 1.9 and/or 2.1 as the regrade code is significantly different.

Patch via github is incoming.