We also had a number of scheduled reports which failed to run after upgrading to v14. After logging a TASK ticket and looking at the logs we realised that this was actually a combination of Tessitura tightening up the security and us changing the user a scheduled report was allocated to - user_id in gooesoft_request.
Each scheduled report has a user_id and and user group id (ug_id). We had updated the user_id for request owned by users who had left. However in doing so the new user was NOT assigned to the user group of the left user. As soon as we updated the user group to a valid one for that user the reports started working.
Therefore might be worth checking that the user and user group combination is valid in Tessitura security.
Alex