A mutual mistake of fact occurs when the parties to a contract have a common intention, but the written contract erroneously reflects the intention due to a mistake on the part of both parties. Lacy v. Ticor Title Ins. Co., 794 S.W.2d 781, 784 (Tex. App.–Dallas 1990), writ denied improvidently granted, 803 S.W.2d 265 (Tex. 1991).