“(1) There must be convincing proof to counteract the evidence of a different intention represented by the document itself; (2) There must be a flaw (that is an operative mistake) in the written document such that it does not give effect to the settlor’s intention; (3) The specific intention of the settlor must be shown; it is not sufficient to show that the settlor did not intend what was recorded; it must also be shown what he did intend; and (4) There must be an issue capable of being contested between the parties affected by the mistake notwithstanding that all relevant parties consent.”