Subject to appeal and subject to vacation as provided herein and in section 524.3-413, a formal testacy order under sections 524.3-409 to 524.3-411, including an order that the decedent left no valid will and determining heirs, is final as to all persons with respect to all issues concerning the decedent's estate that the court considered or might have considered incident to its rendition relevant to the question of whether the decedent left a valid will, and to the determination of heirs, except that:
(1) The court shall entertain a petition for modification or vacation of its order and probate of another will of the decedent if it is shown that the proponents of the later-offered will were unaware of its existence at the time of the earlier proceeding or were unaware of the earlier proceeding and were given no notice thereof, except by publication.
(2) If intestacy of all or part of the estate has been ordered, the determination of heirs of the decedent may be reconsidered if it is shown that one or more persons were omitted from the determination and it is also shown that the persons were unaware of their relationship to the decedent, were unaware of the death or were given no notice of any proceeding concerning the estate, except by publication.
(3) A petition for vacation under either (1) or (2) must be filed prior to the earlier of the following time limits:
(i) If a personal representative has been appointed for the estate, the time of entry of any order approving final distribution of the estate, or, if the estate is closed by statement, six months after the filing of the closing statement.
(ii) Whether or not a personal representative has been appointed for the estate of the decedent, the time prescribed by section 524.3-108 when it is no longer possible to initiate an original proceeding to probate a will of the decedent.
(iii) 12 months after the entry of the order sought to be vacated.
(4) The order originally rendered in the testacy proceeding may be modified or vacated, if appropriate under the circumstances, by the order of probate of the later-offered will or the order redetermining heirs.