Simple Project Manager - Successor Field?

I have installed the Simple Project Manager application from the Exchange and seem to have found an issue with the Successors field. As I understand this field, it is a link to a query that should display records which include the 'Task ID' in the Predecessor's field. Unfortunately, the query in the formula does not generate the results I expected.  Perhaps it is working as intended, however I have documented what I have found below in hope that someone may be able to  confirm whether there is an issue or help me gain some insight as to what I am missing.

Following is a screenshot of the formula for the Successor field.



In the screenshots below. Sample data is shown from the task table indicating that task 59 is a successor of task 58.



 However when I click the link to view the successors of task 58, the report indicates that there are no records, rather than showing task 59 as I expected.




I tried some variations of the formula in an effort to better understand the results.

When HAS is used in place of CT, we see results consistent with CT as expected.


However when XHAS is used, the results return all 41 tasks, INCLUDING task 59 which clearly has task 58 listed as a predecessor.



Perhaps a clue is that when searching the report for 58, only the record 58  with the is displayed in the filtered results, rather than records 58 and 59.

Thank you for reading my post.