Employee's Accumulators/Entitlements reset to 0 after historical edit.

Our Payroll department processed some historical absences for a new hire to change he absence from one take to another after the absences were processed in 1 calendar group. The corrections were made via Absence Event (original absences voided and added new absence take with different code. When the new absence calendar was run and finalized and in reviewing the “Results by Calendar Group” page they noticed that ALL the employee's balances were 0. The employee is now unable to take any absence.

I know we can manually update the accumulators - however, we'd like to know why this occurred.

Has anyone run into this or knows what would cause this?