Sipping the Seder Pesach's 4 Cups of Wisdom

You drink the four cups at the Seder and say the short bracha after the wine, but you forget Yaaleh V'Yavo. Do you go back and say it again? By the usual rule, a bracha is repeated when the meal was obligatory, and the four cups are certainly obligatory. Yet no one seems to rule that way.Rav Shach offers a new angle on what exactly is obligating us that night. Then Rabbi Akiva Eger's teshuvah on women and the matzah seems to push against it, until one more distinction brings the two back together.