1-26D-8. Review of proposed findings or decision--Written reasons for rejecting or modifying findings or decision. The reviewing agency shall personally consider the whole record or such portions of it as may be cited by the parties. If the reviewing agency rejects or modifies proposed findings or a proposed decision, it shall give reasons for doing so in writing. In reviewing proposed findings of fact entered by the presiding hearing examiner, the reviewing agency shall give due regard to the hearing examiner's opportunity to observe the witnesses.