Does a mistake by a secretary or other employee cause a default judgment to be set aside?

Benjamin v. Dalmo Mfg. Co., 31 Cal.2d 523, 527-528, 190 P.2d 593, 595, where a secretary, misunderstanding her instructions, filed the complaint and summons in defendant's office instead of sending them to defendant's attorney, and 'the day following the president's receipt of notice from defendant's attorney regarding the taking of the default judgment, the papers served upon defendant's respective officers were forwarded to the attorney in prompt correction of the prior oversight.' On motion to set aside the default, the trial court held that the delay until receipt of the notice of default was 'satisfactorily explained', but there was 'an unexplained delay' of almost three months 'after full knowledge of the entry of the default.'