Hiya, Ive been following this thread for a while as I've been having the same 'clunking' boot sound on my Octavia hatchback. Ive tried a few of the suggestions here, which alleviated the issue but not entirely. Its been driving me mad. This week I 100% fixed it and just want to share how... As others have said, its the wedge shaped pieces on either side of the boot lid (see pic). As others have also said, there appears to have been a recall at some point. I decided to take a punt on two of these genuine replacement wedges from this UK supplier. https://www.lllparts.co.uk/product/5ja827249d/wedge-buffer-5ja827249d They took about a week to arrive. On delivery, it was clear that the old wedges are very stiff and hard to depress compared to the new ones. I suspect they havn't been cushioning the boot lid enough and just banging against it instead - hence the clunking. I fitted the new ones in about 5 mins and much to my delight the clunking has stopped completely. The rear of the car feels much more solid over speed bumps and uneven road. I can now enjoy driving it again. If your having the same issue, i recommend grabbing a couple of replacement parts from that link. Cheers