Since the accounting workflow introduced Guard on start transition, it is required
   assignee or assignor to change the state (before Modify Portal content was enough).

   The script is invoke as Shadow user, and since destination section is set, the User
   automatically become Auditor (rather them Assignee) so it would imply a deeper
   change to relax security for the shadow user (not shadow person) just to invoke start.
   Not to mention HUGE security update to be done.

   Use Manager proxy role is not ideal, but it doesn't introduce a security issue while
   solve the problem until a deeper review on the roles for Shadow users takes place.