Contingent Worker Number Assignment Duplicates Employee Number

We have an issue where contingent workers are getting assigned numbers that duplicate existing employee/assignment numbers (i.e. they are separate sequences).  This causes an issue when staff are using Data Loader to dump pay element entries into BEE batches from Excel (for mass updates when contracts change, for example).  Data Loader errors out because it doesn't know which person to chose.  Staff said they have the same issue when manually posting a BEE batch (they have to pick between the contingent worker and the employee from a popup of assignment numbers).

In reading ID 1209983.1, Need a Different Employee Number Generation for two Classes of Employees, it sounds like the default for Oracle HRMS is that one sequence number is used for both contingent workers and employees unless you use a custom formula of the type 'Person Number Generation'.  We have no formulas of that type.