(A) Evidence of prior discipline is inadmissible to prove the existence of any incident alleged in a "section 124.34 order."
(B) For purposes of this rule, prior discipline consists only of those written reprimands, fines, suspensions, reductions, or removals contained in the employee's personnel file.
(C) The board may admit evidence of prior discipline if it is offered to prove either:
(1) Notice to an employee that particular conduct is unacceptable; or
(2) A continuing problem justifying harsher discipline than might otherwise have been imposed.