From MoodleDocs

The message 'Can not find data record in database table' is displayed when a forum post or other data has been deleted.

If you have recently upgraded and obtain the message, try running Cron repeatedly until you see the message "Running clean-up tasks..." near the top of the output. See the Can not find data record in database table context discussion for further advice. If that doesn't help, enable debug messages, developer level and recreate your error. This gives you some extra handles to solve the problem.