Hi Jonathan,
I'm using Moodle 2.9.2 and also have this type of error sometimes.
I don't exactly know what to do for that...
I can also see these errors in mdl_backup_logs :
SELECT FROM_UNIXTIME(timecreated) AS Date, backupid, message
FROM mdl_backup_logs
WHERE loglevel=20 AND message LIKE 'backup_auto_failed_on_course%'
ORDER BY timecreated DESC
LIMIT 20;
SELECT FROM_UNIXTIME(timecreated) AS Date, backupid, message
FROM mdl_backup_logs
WHERE message LIKE 'Exception%'
ORDER BY timecreated DESC
LIMIT 20;
These queries indicate messages about the same backups (Date and backupid's are the same).
Séverin