How can I get more details about a Scheduled Jobs failure?
I would recommend looking in two other places:


The CiviCRM error log. This is to be found (for Drupal) in sites/default/files/civicrm/ConfigAndLog/CiviCRM.(long number).log 
The PHP error logs. This is different for each server / Control Panel so I'm afraid I can't give more specific directions than that. 


Make sure you find the place in the logs which matches the time that you triggered the job, to save you trawling through many lines of text. I would suggest you trigger the job one more time, take note of when you did it, and then look up what happened in those two places at that time.