155 is no time to panic. Meat rises quickly in the beginning. Rising to 155 in that amount of time is not at all unusual. You were no where near the stall. I think if you had just left it alone, without opening the door, turning it down, etc., it would have ended up completing the cook in about the same amount of time. Once it got to 165 or so, it would have stopped rising so quickly. It would probably sit in the 165-180 range for SEVERAL hours, probably not going up more than and few degrees, and the temp might even go down for a while. This is one of the things I see most commonly, is panic at the quick rise in the first few hours.