Mo. Rev. Stat. § 473.077: Proceedings reopened, when.

If the court determines the facts as provided in section 473.073, its order shall be final, subject to the following exceptions:

(1) It may be reopened at any time, within six months from the date of the first publication of notice of letters, for the purpose of admitting a will to probate not theretofore presented to the court except that, if a previous will has been probated or rejected, it may not be reopened after the time for bringing a proceeding under section 473.083;

(2) It may be vacated or modified for good cause as provided in section 472.150;

(3) The finding that the alleged decedent is dead is not final or conclusive.