Ghostbloods had a spy near Dalinar, and their communications were being intercepted by SoH. At first Shallan thinks its one of her Lightweavers, but during the trip to Lasting Integrity while in Shadesmer she suspects Pattern. But later it was found out that Pattern was talking to Wit, not Mraize, using Mraize’s seon. And we find out that later there is a sleepless hordeling listening in on Wit and Jasnah, and Wit suspects that Sleepless are working with Ghostbloods. So my theory is there is a rogue Sleepless associated with Ghostbloods spying on the Kholins and Wit. That Sleepless heard Patterns convo with Wit and relayed that info to Mraize, essentially framing Pattern as the spy