Is there native way to log failed scheduled tasks, or indeed any task with a status which isn't 0x0, in Event Viewer, or will this need a custom script to scan the log or something?I'm looking to ...

This post explains Audit Success or Failure in Event Viewer generated by changes to accounts, objects, policies, privileges, & other system events.

If you see Event ID 55, 50, 140, or 98, The file system structure on the disk is corrupt and unusable in Event Viewer on Windows; follow this guide.