Short Answer: The thermal cut-off kicked in. Read on... There is a thermal cut off switch that prevents the roaster from getting too hot. It's a safety precaution, and every home roaster has something of the sort ... even air popcorn poppers have them. Sometimes it can stop the roast from progressing, for about 30 seconds ( it turns off the heating coils), but then the roaster will rapidly come back up to temperature. When it recovers the roaster will reach a higher temperature than the first thermal cut-off event, but it will, once again, activate at some point. I have tested many units to find the real-world temperature cut-off point, and there is a range between 440 (only 1 tested that low) and 465 farenheit, measured with a bean probe. There is a way to easily adjust the position of the thermal cut-off sensor to a higher position on the roast chamber, meaning it will kick in only at a higher temperature. My video on how I modify roasters for testing touches on this. It works, but I can't recommend it since it voids the warranty if you modify the roaster. If you experience a roaster that doesn't finish first crack before the thermal cut-off kicks in, definitely check out the video and article about roast curves. If it is still a problem contact info@sweetmarias.com