Getting Error (HR_6881_HRPROC_ORA_ERR ORA-06512)

Content

I have an extract where I had to write a fast formula to find out rehire date as per customer's requirement:

The Formula which I have written is given below:

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DEFAULT_DATA_VALUE FOR PER_EXT_PAY_HR_REL_DATE_START IS '1951/01/01 00:00:00' (DATE)
DEFAULT_DATA_VALUE FOR PER_EXT_PAY_HR_REL_ORIGINAL_DATE_OF_HIRE IS '1951/01/01 00:00:00' (DATE)

I=1
J=1

WHILE PER_EXT_PAY_HR_REL_DATE_START.EXISTS(I)LOOP
(
DATE1= PER_EXT_PAY_HR_REL_DATE_START[I]

  WHILE PER_EXT_PAY_HR_REL_ORIGINAL_DATE_OF_HIRE.EXISTS(J)
  LOOP
  (
  DATE2= PER_EXT_PAY_HR_REL_ORIGINAL_DATE_OF_HIRE[J]