what kind of a gate is it? we have a gate with vertical slats only, about 36", and my adult cat will not climb it nor does he jump over it. Is your gate like checkerboard, so they can climb it (literally?)
you need a new gate.. can you return this one and get something else? btw, i remember searching for a gate for marsh, and we didn't find even ONE which had slats close enough for a young kitten NOT to go through. We had to buy a standard one and fashing a piece of clear figerglass on it until he grew.