In case this helps others: I was having random USB connect/disconnect issues for devices plugged into the Surface Dock. It turned out that one of the "springy" pins -- the top left one as you look at the socket -- was bent. A loupe and sewing needle fixed the bend, and the random USB issues stopped. The magnet on the dock plug is very strong, and it causes the connector to snap into the socket quite violently. This likely caused the issue. The connector socket seems very fragile. The bend happened again, and my needle repair broke the springy part off. Now everything works fine, so maybe the springy part was just a retainer. I don't want to send the Surface Book in for repair, because it'll likely take 2-3 weeks. But will do so before the warranty runs out.