Clunking/Rattling noise while breaking/coasting

We purchased our 2017 Bolt Certified preowned and it has made a clunking/rattling noise since we got it a year ago. Our warranty is up in a few weeks and we’re desperate to get this figured out before the warranty is up! We’ve brought it in several time but the dealership just says they can’t reproduce the sound. It’s most noticeable on uneven/bumpy roads when going downhill breaking or coasting. I don’t notice it when accelerating. I sent a video to the dealership but they say it’s just road noise but it is definitely not. They want to hear it in person but will only go so far from their dealership and all the roads around the dealership are newer and smooth. Anyway, any ideas what this noise could be or how I can convince them to do something about it??
New to the site so not sure how to upload a video so I made it into a YouTube video. Any suggestions are appreciated!