Arbitrator heard a three-party dispute over a failed chiller at a municipal ice rink, sitting as the sole neutral chosen jointly by Owner, Contractor and Manufacturer. Arbitrator took evidence for four days and wrote the award. Two years later Arbitrator returned to private practice, and Contractor asked Arbitrator to bring a fresh suit against Manufacturer arising out of the same chiller failure. Arbitrator described the earlier role in detail to Owner and to Contractor, including what the hearing had revealed, and each of them signed a letter of agreement. "We stand on our rights and we object," Manufacturer's general counsel wrote back. Arbitrator accepted the engagement, filed the suit in the county court, and sent the file to a paralegal who had handled the arbitration billing. Is Arbitrator subject to discipline?