Are you loading very close to the lands? If you are, it's possible one maybe slipped by you when you were seating the bullets and it was a tick longer OAL and since you are already on the high end of the load range with H1000, it doesn't take much to spike up the pressure.
Defensive Edge has done a lot of work with the 338 Edge and you are a full grain over his load with H1000 and a 300gr Berger.
Jewel makes the finest trigger available but that are not the most robust trigger, that is for sure, and they are prone to problems like you experienced with a hot load.