Absence of nullity of the arbitration award in proceedings that required robust evidentiary proceedings with the need for the arbitral tribunal's intervention to, by mutual agreement with the parties, set new terms for the stages of the arbitration proceedings. Allegation of unlawfulness of the criterion adopted by the expert witness for the determination of the assets. Issue that merges with the merits and cannot be reviewed in a rescissory action for nullity of an arbitration award: