Assignment change date with primary flags cannot be updated once entered

A new assignment, E218284-2, was created using the Add Assignment transaction with an effective date of 08-Sep-2026. This assignment was initially designated as the primary assignment.
The business requirement is for this assignment to start on 02-Sep-2026 instead of 08-Sep-2026.

Cannot correct the start date (not available) and cannot delete the assignment as it is now primary.

The assignment start date is not available for correction in the UI. The assignment also cannot be deleted because Oracle HCM returns the following error:
PER-1531533: This assignment became nonprimary when a new primary assignment was selected.

We used HDL as work aroung to change the dates, but customer is using the multiple assignments so they want to do the date changes from the UI.