Tasks failure (The Apple Event Handler Failed)
 

AppleScript root-level tasks (directly under a document) don't get populated, and attempting to enumerate them throws an error -10000 (the Apple Event Handler Failed)

The 'task' relationship on 'document' is there only to allow object specifiers for tasks elsewhere to be 'id' based ('task id "xyz" of document id "qrs"'). The document doesn't directly contain tasks, but it _does_ contain 'inbox tasks', so you should be able to access those directly).

I hope this helps!