I took a closer look at my PBV6PSE. I was able to get a grate in the center to fall through by pushing down directly on the front right corner of the grate. It took quite a bit of force, but when it happened it quickly popped through.
The wall and support will flex out when this happens. Guestimating, it took about 20 lbs of side force (not down) to flex the wall enough to clear the grate.
The grates measure 22-1/4". The inside wall-to-wall measures 22-1/2". There is about 1/4" that needs to flex to get the grate to slip down.
I took a few pics of what I see.
To remedy this, I would get some pieces of 1/8" 3/4"x3/4" angle steel. Cut lengths to as long as possible (tight against the rear wall and almost touching the door when closed), and rivet or screw it to the wall just above the shelf. Place screws/rivets as close to the ends as possible, then evenly space three more along the angle's length. The idea is to stiffen the supports so they don't flex out and are supported by the angle steel ends supported by the end walls. A bonus of this mod would be to prevent the shelf from tipping down as you pull them out, and IMHO is an oversight on the design. As an alternate, you could mount the angles to directly support the shelves with the angles installed on top of the shelf supports.
I'd make sure when drilling to not hit any wires inside the walls. There's only a few and they generally run straight point-point.
I haven't had issues with grates falling through and have done quite a few briskets up to ~20 lbs. That's not to say there are not any units out there where the tolerances have stacked up to give the issue that you have.
Please respond with how you proceed.
