What process could cause all Assignment Supervisors to receive an effective end date?

Summary:

All Assignment Supervisors unexpectedly received an Effective End Date in Production. Therefore there was no Manager Hierarchy displaying. Assignment records did not have a Manager.

Note, there was no effective date change to the Assignment.

The problem has since been corrected (via HDL), however we still do not know the cause of the issue.

Content (required):

* Assignment Supervisor EFFECTIVE_END_DATE for all = 2022-06-20T00:00:00.000+00:00

* The LAST_UPDATE_DATE of the first record that changed was: 2022-06-20T11:00:53.448+00:00

* The LAST_UPDATE_DATE of the last record that changed was: 2022-06-20T11:10:26.992+00:00

* All last updated by the same user