Except as provided in § 29–409 of this article, if, because of an error, a retiree or beneficiary receives a benefit that differs from the benefit the retiree or beneficiary is entitled to receive, the Board of Trustees shall: correct the error; and to the extent practicable, adjust the payment to the retiree or beneficiary to provide the actuarial equivalent to which the retiree or beneficiary is correctly entitled. Notwithstanding § 21-502 of this title, the Board of Trustees may recover the amount of any improper payment. After due notice, if a person who receives an improper payment fails to repay the money owed, the Board of Trustees may: begin an action to recover the amount of the improper payment and the costs of bringing the action; or adjust any future monthly payments of that person's allowance to recover the amount owed. Subject to the approval of the Board of Trustees, the Executive Director of the State Retirement Agency shall: determine any monthly adjustment under paragraph (2)(ii) of this subsection; and notify the person of the total amount to be recovered, the monthly adjustment, and the period of recovery.