The board shall order the collector to cancel or modify, as may be proper, an assessment when it finds that any property has been either:
(a) Assessed in any year more than once.
(b) Assessed by reason of a clerical error for more than its full cash value.
(c) Computed for assessment on an excessive acreage.
(d) Assessed while not in the district.
(Added by Stats. 1959, Ch. 2041.)