The Probate Judge can correct or reform a will or trust if it is clear that "an error was caused by a scrivener's or draftsman's failure to embody the true agreement of the parties in a written instrument." So, the question always is - does the will or trust show the true agreement of the parties or did the scrivener or draftsman (the attorney) make a mistake.
A 2019 case showed the problems that the courts can encounter. A man and woman got married. The wife had a child "Edna" who the husband adopted. They later had two more children, Ignacio and Esperanza. They created a trust through their attorney. In the trust, they said we have two "children" and named Ignacio and Esperanza. The problem was that that definition was the only place in the trust where they used the word "children." The rest of the trust disposing of their property refered to their "descendants".