My 2016 back captains chairs were rattling and I found a temporary fix. I installed 2 short pieces of bicycle inner tube attached to the latch rod on floor with tie wraps. Seat is a little hard to latch down but does work if pushed firmly. Wrapping with layer of electrical tape might work better but haven't tried that. I did previously install the washers under the floor attachment pan bolts as recommended on a YouTube video but that didn't fix it. Made no sense as to how it would but I tried it anyway and didn't help.I have this problem on my '21 Denali and it drives me nuts. If someone or something is in the seat then the rattle stops. Also if the seat is folded up it won't rattle either. At first I thought it might be the levers/handles so I put a piece of felt on the back of them but that didn't fix the problem. I think it might be under the seat in the base but I haven't been able to pinpoint it. It's definitely a plastic on plastic sound.