California Code, Probate Code - PROB § 8924

(1) The personal representative shows cause, including incompetence or undue delay in making the appraisal, that in the opinion of the court warrants removal of the probate referee. The showing shall be made at a hearing on petition of the personal representative. The personal representative shall deliver pursuant to Section 1215 notice of the hearing on the petition to the probate referee at least 15 days before the date set for the hearing.

(2) The personal representative has the right to remove the first probate referee who is designated by the court.Cause need not be shown for removal under this paragraph. The personal representative may exercise the right at any time before the personal representative delivers the inventory to the probate referee. The personal representative shall exercise the right by filing an affidavit or declaration under penalty of perjury with the court and delivering a copy to the probate referee pursuant to Section 1215. Thereupon, the court shall remove the probate referee without any further act or proof.

(3) Any other cause provided by statute.