In what circumstances will the Supreme Court of Canada strike down a contract where the contract states that the contract does not contain a clause requiring full payment?

In these circumstances, it is not surprising to see comments such as the following taken from the minority opinion of Adam Wilson J., dissenting in Gardiner v. Ford (1863), 13 U.C.C.P. 446 at pp. 449: In this instance, as in many others, the rule of reason will at last prevail, that if the parties do in truth agree that a smaller sum than the sum demanded shall be taken in full, that effect will be given to the bargain which they have voluntarily made, rather than to any fanciful rule of law, laid down at a time when the fashion was to thwart all contracts, unless the courts were allowed the further privilege to make others in their stead. When a smaller sum can be pleaded in discharge of a greater, if paid after action commenced, or if paid by a negotiable note, even before action brought, we may hope soon to see the like sum when paid in money held to answer every purpose quite as well as a note, and the payment of it before action brought to be rather more advantageous for the parties than after litigation begun. I think we should in this country be prepared to act upon a reasonable rule, whenever we are convinced it is reasonable, and not consider ourselves bound unthinkingly to follow the English decisions through all their phases, until the first erroneous case has been over-ruled, and more particularly when we see the inevitable tendency of such decision ...