Moodle 3.9.6+ (Build: 20210423)
Issue: Most quizzes are giving 500x server errors when a quiz question is answered and the "Check" box is clicked. We have found one quiz that works while the others we have tested give this error.
Checked the server and it has 19gb free so storage doesn't seem to be a concern. Server cache purge was completed (Admin > Development > Purge all caches) .
Turning on developer mode causes the site to become virtually unusable with pages timing out or loading very slowly. Also we are not seeing additional log entries (Admin > Reports > Logs) when this mode is active that display error data.
We updated Moodle to version 3.9.6 last month on 5/19 but the student complaints for broken quizzes just started coming in over the past week. The courses with broken quizzes have been around for years so this is not a new content or config issue.
If anyone has suggestions on how to proceed from here that would be much appreciated.