Thanks.
It took some time to hear back from our overworked
server admin. He has sent me a log file. I am including stuff related to autosubmission, that looks suspicious.
"Processing 7 assignment submissions ...
Processing assignment submission 83741 ...
ERROR: handle_notification_sent - incomplete settings
Done
Processing assignment submission 83740 ...
ERROR: handle_notification_sent - incomplete settings
Done
Processing assignment submission 78530 ...
ERROR: handle_notification_sent - incomplete settings
Done
Processing assignment submission 83252 ...
ERROR: handle_notification_sent - incomplete settings
Done
Processing assignment submission 83238 ...
ERROR: handle_notification_sent - incomplete settings
Done
Processing assignment submission 83222 ...
ERROR: handle_notification_sent - incomplete settings
Done
Processing assignment submission 83233 ...
ERROR: handle_notification_sent - incomplete settings
Done
Done processing 7 assignment submissions
... used 77 dbqueries
... used 1.9326550960541 seconds
done."
and
"Processing module function quiz_cron ...
Looking for quiz overdue quiz attempts...
Error while processing attempt 32928 at 325 quiz:
Illegal formula syntax starting with '{L1}'
#0 /var/www/html/moodle/question/type/calculated/question.php(71): qtype_calculated_variable_substituter->calculate('(1-exp(-(1.1)*0...', '6', '1')
#1 /var/www/html/moodle/question/type/calculated/question.php(170): qtype_calculated_question->calculate_all_expressions()
#2 /var/www/html/moodle/question/type/calculated/question.php(60): qtype_calculated_question_helper::apply_attempt_state(Object(qtype_calculated_question), Object(question_attempt_step_read_only))
#3 /var/www/html/moodle/question/engine/questionattempt.php(1517): qtype_calculated_question->apply_attempt_state(Object(question_attempt_step_read_only))
#4 /var/www/html/moodle/question/engine/questionusage.php(941): question_attempt::load_from_records(Object(my
sqli_native_moodle_recordset), '489785', Object(question_engine_unit_of_work), 'deferredfeedbac...')
#5 /var/www/html/moodle/question/engine/datalib.php(469): question_usage_by_activity::load_from_records(Object(mysqli_native_moodle_recordset), '41724')
#6 /var/www/html/moodle/question/engine/lib.php(84): question_engine_data_mapper->load_questions_usage_by_activity('41724')
#7 /var/www/html/moodle/mod/quiz/attemptlib.php(569): question_engine::load_questions_usage_by_activity('41724')
#8 /var/www/html/moodle/mod/quiz/cronlib.php(78): quiz_attempt->__construct(Object(stdClass), Object(stdClass), Object(stdClass), Object(stdClass))
#9 /var/www/html/moodle/mod/quiz/lib.php(598): mod_quiz_overdue_attempt_updater->update_overdue_attempts(1598097890, 1598097830)
#10 /var/www/html/moodle/lib/classes/task/legacy_plugin_cron_task.php(93): quiz_cron()
#11 /var/www/html/moodle/lib/cronlib.php(105): core\task\legacy_plugin_cron_task->execute()
#12 /var/www/html/moodle/lib/cronlib.php(67): cron_run_inner_scheduled_task(Object(core\task\legacy_plugin_cron_task))
#13 /var/www/html/moodle/admin/cli/cron.php(61): cron_run()
#14 {main}
...
...
...
Considered 35 attempts in 3 quizzes.
Starting quiz reports
Processing cron function for quiz_statistics...
... started 17:34:52. Current memory use 195.6MB.
Cleaning up old quiz statistics cache records...done. (1 dbqueries, 0 seconds)
Finished quiz reports
... used 2262 dbqueries
... used 2.0344040393829 seconds
done."
I do not know which course it corresponds to, but it sounds like one of my colleagues has an error in this quiz. There is nothing else in the file pertaining to quizzes (just some deletion of quizzes in one particular course). Unfortunately, the problems (happened this morning for several courses as well) were not captured in the log as the sysadmins had switched off logging earlier (they are concerned about the size of old logs), and they finally switched it on only on my request after the previous problems had resolved over a period of 4-5 hours:
One thing they noted was that the overall Moodle cron job is taking 150 minutes (isn't that high?). The University is running around 650 courses (as gleaned from Insights analysis error messages in the log).