Keep asking those questions! We love to hear them. When taking any meat to 195, it's going to rise very quickly to 150. So I'm not surprised it got there fast. 150 for Chuck Roast is pretty low, unless you are chilling and doing really thin slices for sandwiches (in which case you would only take it to about 130 for medium rare). You really want a Chuck Roast to go to 190-200 for eating as a roast, where the collagen can convert to gelatin, giving you that super tender gelatinous mouth feel, and fall-apart juicy meat. The "stall" is going to occur sometime between 160 and 180, which is where the temperature of the meat is going to sit... or even go down, for a very long time. So next time, for a long cook like that where your internal meat temp needs to go to the 190-205 range, like for Chuck Roast, Butt, Brisket, etc., don't panic and turn down the dial when the temp rises very quickly in the beginning. Leave it at 225. You'll see that it slows down, and practically stops, for several hours.