I know when things go wrong, it can be very frustrating... It sometimes can make you want to throw in the towel and move onto something else... I think, if You would retrace your steps on this cook, you would see what issues and perhaps missteps that caused this flameout. From reading your post, the problem was with your preheating procedures/steps. I posted on another forum site last year on how to prevent flameouts from happening on PB Pellet Grills... I almost had the same exact problem happen to me, but I was able to clear out the fire pot and all the pellets that had spilled over into the bottom of the pellet grill before the explosion occurred. I figured out that I didn’t preform the required Preheating Procedures and I just went and plugged in the grill and dialed in my desired temp... ie.. Set it and Forget it... Big Mistake.. I had to figure out that my PB Austin XL requires at least a 20-30 min. preheating. As per the Owners Manual, turn the grill on first and set it on P4 and the Smoke setting with the lid open and wait til the ignition has started, then I needed to preheat at a minimum 300* degrees for 20-30 mins. and once the grills temps settles and stabilizes at a solid 300* degrees, then I could set my grill to my desired temp after that. I believe your Owners Manual says to preheat your PB 820 on the high setting... I would next time dial in your P-setting and wait for the pellets to ignite with the lid open, then once the ignition has started, I would preheat at 300*-350* degrees for a minimum 20-30 mins. and let the grills temp settle and stabilize. Also, ensure the pellets in the hopper are flowing through the Auger Tube and into the fire pot smoothly. A Hopper full of pellets and a good stirring of the pellets really helps. That was back in June 2018 and I haven’t suffered a Flame Out since. I always say, Never take short cuts in the proper preheating procedures and operation of any Pellet Grill. From what I read in your posting, You just turned your grill on and set the temp to 250* degrees for 30mins. Something as simple as not preheating your grill correctly each and every time can cause flameouts to happen. Sometimes we can get away with shortcuts, but it only takes that one time and then we find out the hard way of what could happen. These Grills are so much like an oven, but they burn wood pellets and our ovens in our homes do not... Your PB 820 is a Non PID Controller Pellet Grill, so Preheating is crucial in the prevention of flameouts and wild temp swings... I wouldn’t give up on your grill just yet... Only You know what you did and didn’t do correctly on this particular cook. Good luck and I’m sure You’ll figure out what happened. Don’t give up, it’s a simple fix and correction.