Temp control was obviously an issue. That you were cooking a flat only played a role because of all the fat of the point rendering and keeping the flat moist. However, the 195 and probe tender is interesting. What was your process after you removed it from the cooker? The current best practice is to let it rest on the counter until it cools to 170, and then wrap and hold for a period of time (1-2 hours) before serving. Another issue can be slicing too much of the meat at once. Brisket needs to be sliced to order and consumed right after slicing. If you cut up the entire flat, it will dry out faster that you would believe is possible.