Russell’s paradox is often incorrectly flagged as contradictory. A contradiction occurs when the answer to a yes/no-question is both yes and no, or like the Khmer like to say, cheh nung choh, or in French, la chose et son contraire.
Russell’s paradox is not contradictory but undecidable or uncomputable, meaning: it is not possible to determine the answer. An undecidable problem is never contradictory. For an algorithm to be contradictory, the algorithm must answer yes but also answer no, depending on irrelevant circumstances. By definition, an undecidable question is never contradictory because the algorithm never answers at all.