The challenge of a contractual arbitration award (arbitrato irrituale) for essential error is admissible when the formation of the arbitrators' will has been deviated by an altered perception or false representation of reality and the factual elements submitted to their examination, and not when the deviation concerns the evaluation of a reality whose elements have been exactly perceived.
The burden of proof regarding the existence of essential factual error for the purposes of annulment of a contractual arbitration award (arbitrato irrituale) lies with the party challenging the award.
Any incompatibility of the arbitrator does not constitute grounds for annulment of the contractual arbitration award (arbitrato irrituale) under article 808-ter of the Code of Civil Procedure, nor for nullity, as the institute of arbitrator recusal is not applicable.