There is an error in the CalculateDays function of the DateHandler library. Additional variables (bh11, bh12, nbh11, nbh12) need to be added to support the "extra" bank holidays on the XXBankHoliday subforms. The PopulateHoliday function instantiates 12 variables, but CalculateDays only checks 10 of these.
Otherwise any holiday entered in the "Additional Day" fields of the BankHoliday form will be skipped and counted as a working day on leave requests.