After exchanging several emails with PB Tech Support, they finally sent me a new, upgraded controller with 'L02' firmware. That is, when first plugged in, 'L02' appears momentarily (maybe, 2 seconds) on the controller display panel.
They had me check all kinds of ridiculous things first like smoke cap to smoke stack distance, for voids in the pellet tunnel, quality of pellets, etc. They also had me time, while on the P4 smoke setting, the time the augur fed pellets vs the time it was inactive. Apparently, on the P4 smoke setting, the augur is supposed to operate every 115 seconds and be on for 18 seconds. Mine rested for an average of 115 seconds but was only on for an average of less than 16 seconds. It was when I reported this finding that they sent me a new controller board.
It was super easy to install the new controller once I got the screws loose from the bottom of the pellet hopper. Apparently they have a gorilla tightening those screws. Almost stripped one of them.
With the new controller board installed, I did an 18 hour port butt smoke that went flawlessly. However, I noticed that at least twice, the internal probe temperature fell below 170 F while I had the set point at 225 F. With the old control board, this is where the death spiral began, the fire pot became overloaded with pellets and the fire was smothered. Interestingly, with the new controller, it seems as if it takes the grill through a 're-ignition' sequence. I concluded this because each time the temp fell to below 170 F, then within 5 minutes, thick smoke began billowing out of the grill as it does in the initial ignition sequence just prior to the fire catching. As this happens, as you might have guessed, the temperature spikes way above the set point - 380 F - because of the large amount of pellets in the hopper. Within 10 - 15 minutes it settles back in to a normal temperature deviation and no flameout.
I can only conclude from this that PB has upgraded the L02 controllers to include a low temp re-ignition sequence to compensate for loss of ignition for whatever reason. My second conclusion is that they likely shipped a lot of these L01 controller grills to Lowes and other big box stores hoping they would work as is. Apparently, many do.
I give the PB tech support guys big props for working with me to solve this problem but take away 1/2 star for not getting to the issue sooner since I told them it was an L01 controller.
I hope everyone else who bought a PB 820 PS from Lowes gets this problem resolved. It's a pretty sweet grill for the money and makes a helluva good pork butt.
Edit 7/1/2022: I’m still rather peeved that I’m having flameout/reignition sequences sometimes. Trying to smoke some pork ribs and noticed smoke billowing out of my PB grill. Checked my ambient temperature and it peaked at nearly 400F and stayed above the set point for 20 minutes. So my ribs cooked for 15 mins instead of smoked. I’ll be looking at alternatives to PB soon.