To stop LWOP overriding a public holiday payment, you will need to adjust the configuration of Leave Without Pay.
Go to Admin.
Select Configuration, then Accrual Types.
Select Leave Without Pay, Edit.
Remove the tick from Overrides Public Holidays, Save.
Note: This part of the product is not date driven, once the change takes place it will impact previous calculations, there will be adjustments for previous periods.
Important: A manual change to remove the backpay calculation will be needed for employees that had been on LWOP on a public holiday.