The Court shall excuse any person from services as a juror if the person is entitled to and requests exemption for any reason specified in O.R.S. 10.050. The Ccourt may also excuse any person from service as a juror either by removal of his or her name from the jury panel or by excuse for a particular time for reason of illness, disability or undue hardship. No person shall be required to serve as a trial juror at more than 3 trials during his or her term of service. No challenge shall be made or allowed to the panel or to the preliminary jury list, and substantial compliance with the requirements of the ordinance shall be sufficient. If at any time the court deems the number of qualified and unexcused jurors on the panel to be insufficient, the Court may cause additional names to be chosen in the aforesaid manner from the preliminary jury list and added to the panel.