“The principle of effective interpretation of the contract, or how important it is to be sure that there is exactly what the parties agreed on, or thought that they had agreed on” — Tatyana Tereshchenko for Zakon.ru
Obscurity or ambiguity of the disputed text, especially when the positions of the parties in the case are also unclear, creates the risk of choosing a "negative scenario", i.e. recognition of the contract as not concluded, invalid, unenforceable, absurd or such as the parties could not even imagine.
However, the choice of such a scenario is a last resort, the use of which must be argued. This is not directly indicated in article 431 of the Civil Code of the Russian Federation (very sorry), but it follows from its meaning (the requirement to establish the actual will of the parties) and the goals of legal regulation (stability and predictability of civil turnover, respect not only for freedom of contract, but also commitment to the consequences of binding the obligation that has arisen). Why is this so?
If a contract is concluded, it is logical to assume that its occurrence has a cause and purpose. Since the contract as a legal fact is a volitional action.
Arbitrary (too fast) recognition of any essential condition as inconsistent or invalid contradicts the stability of the civil contract and the general idea that contracts must be respected (parallel with pacta sunt servanda). Actually, the roman principle favor contractus is also about this – about the need to favor the transaction "to be" in every possible way.