Unless required for the disposition of ex parte matters authorized by law, the executive director, the administrative law judge, and any member of the board who may render a decision that may become final under this chapter or make findings of fact and conclusions of law in a contested case may not communicate, directly or indirectly, in connection with any issue of fact or law with any agency, person, party, or their representatives, except on notice and opportunity for all parties to participate. To the extent permitted by law, the executive director, the administrative law judge, and any member of the board who may render a decision that may become final under this chapter or make findings of fact and conclusions of law in a contested case, may communicate ex parte with employees of TRS who have not participated in any hearing in the case for the purpose of utilizing the special skills or knowledge of TRS and its staff in evaluating the evidence.