Halachicly speaking, if an error is found in a Psak Din or if new information comes to light, the decision can be revoked (see ch"m 25:1-3) by the initial beis din or by one of greater authority.
Although the Gemora (Bava Basra 138b) states that one beis din need not check up after another beis din, at a time that batei din are less qualified, there is halachic basis for a more qualified beis din to review the decision of another beis din (see Pischei Teshuvah Ch"M 19:3). In absence of a beis din hierarchy however, this is hardly an easy route to take. This is especially true if the arbitration agreement includes a clause which precludes the option of an appeal, leaving a dissatisfied party without recourse.
Additionally, once the tribunal has issued its decision its members become functus Officio and they are legally no longer in the position to change the Psak Din.
A way around this would be to offer the parties the option to first receive an indicative ruling. This would allow them to complain to the arbitral tribunal within an agreed period of time before it issues a final Psak Din.