Alright, I've been dealing with this for a while and I think it's finally time to figure out what's up with it. I have a 2003 Accord coupe, and whenever I lean or push on my quarter panels, they'll bend in super easily. Drivers side has a dent because of this, but it's easily popped out but also easily popped back in. My friend said that there's some kind of stick on foam blocks or something that Honda makes to support the inside of the qp, but I can't find any of those. I've felt plenty of other accord coupes, and none of them seem to have the same flex as mine. So, what I'm asking is, what are these foam blocks if they exist, and what other ways could I support the quarter panel? I'm just worried something will fall into it or it'll get pushed in too hard and permanently dent in.

 

that thing can be fixed only if you strip the door panel and inspect the interior area. After that you will see whats causing the problem.

There are a lot of youtube videos demonstrating door panel stripping so you can try it with a help from a friend.