Reviewing attempt steps fails with the following error:

Coding error detected, it must be fixed by a programmer: $seq out of range

Enabling PHP errors reveals the following details:

Notice: Undefined variable: seq in /home/anttix/products/moodle/2.1+/question/engine/questionattempt.php on line 1204 Call Stack: 0.0001 623680 1.

() /home/anttix/products/moodle/2.1+/mod/quiz/reviewquestion.php:0 0.1193 6124912 2. mod_quiz_renderer->review_question_page() /home/anttix/products/moodle/2.1+/mod/quiz/reviewquestion.php:104 0.1659 8530520 3. quiz_attempt->render_question_at_step() /home/anttix/products/moodle/2.1+/mod/quiz/renderer.php:80 0.1660 8530600 4. question_usage_by_activity->render_question_at_step() /home/anttix/products/moodle/2.1+/mod/quiz/attemptlib.php:968 0.1660 8530600 5. question_attempt->render_at_step() /home/anttix/products/moodle/2.1+/question/engine/questionusage.php:375 0.1661 8533704 6. question_attempt->render() /home/anttix/products/moodle/2.1+/question/engine/questionattempt.php:732 0.1668 8546856 7. question_behaviour->render() /home/anttix/products/moodle/2.1+/question/engine/questionattempt.php:702 0.1674 8559760 8. core_question_renderer->question() /home/anttix/products/moodle/2.1+/question/behaviour/behaviourbase.php:127 0.2399 8650240 9. core_question_renderer->response_history() /home/anttix/products/moodle/2.1+/question/engine/renderer.php:92 0.2424 8665024 10. question_attempt_with_restricted_history->__construct() /home/anttix/products/moodle/2.1+/question/engine/renderer.php:387

Coding error detected, it must be fixed by a programmer: $seq out of range

More information about this error
Stack trace:

line 1204 of /question/engine/questionattempt.php: coding_exception thrown
line 387 of /question/engine/renderer.php: call to question_attempt_with_restricted_history->__construct()
line 92 of /question/engine/renderer.php: call to core_question_renderer->response_history()
line 127 of /question/behaviour/behaviourbase.php: call to core_question_renderer->question()
line 702 of /question/engine/questionattempt.php: call to question_behaviour->render()
line 732 of /question/engine/questionattempt.php: call to question_attempt->render()
line 375 of /question/engine/questionusage.php: call to question_attempt->render_at_step()
line 968 of /mod/quiz/attemptlib.php: call to question_usage_by_activity->render_question_at_step()
line 80 of /mod/quiz/renderer.php: call to quiz_attempt->render_question_at_step()
line 104 of /mod/quiz/reviewquestion.php: call to mod_quiz_renderer->review_question_page()