The approval by the court of a testamentary trustee's account after due notice and service of papers or representation as provided in this chapter, shall, subject to the right of appeal, relieve the trustee and his sureties from liability to all beneficiaries then known or in being, or who thereafter become known or in being, for all the trustee's acts and omissions which are fully and accurately described in the account, including the then investment of the trust funds. The court may disapprove the account and surcharge the trustee for any loss caused by a breach of trust committed by him. The account may be reopened by the court on motion of the trustee or a beneficiary, for amendment or revision, if it later appears that the account is incorrect, either because of fraud or mistake. Court approvals or disapprovals of intermediate or final accounts shall be deemed final judgments in so far as the right of appeal is concerned. No account shall be reopened because of a mistake more than one year after its approval. No beneficiary may move for the reopening of any account because of fraud more than 90 days after he discovers the existence of the fraud.