What responsibility does a successor trustee have to correct errors that were made in prior years by the initial trustee?
A trustee's "fiduciary duty" would require him or her to try to correct material (important) errors made previously that affect the rights (e.g. how much everyone gets) of the beneficiaries. The trustee could hire, and pay for via the trust, necessary expert help to do (such as a CPA), so long as the amount paid therefore is reasonable.