It’s possible that the CF sheets were properly laid, but the resin did not get uniformly infused into the layup. Usually, a vacuum is used to “suck” the resin into the layup so that it is uniformly infused. Sometimes things don’t go as planned. That would leave a void or a section where the CF would be “dry” and brittle, and therefore degrade over time. Only way to tell would be to cut it open.
Such voids are fairly common in all types of fiber reinforced plastics such as fiberglass and carbon fiber.
All-in-all you were fortunate to get a new frame so quickly. Even if they didn’t contest it, it may have still taken that long to get it.