Absolutely take your car back to where you’d purchased with the diagnostics. Good on you for taking it somewhere other than purchasing location. If they don’t respond, let them know you’re seeking legal counsel. The right letterhead can often get things in motion.
Fun bmw story. About 6 years ago I had a similar noise coming from my X5, and then sunroof was intermittently not working. I took it to the dealership that day. The final answer… new sunroof. Thankfully I had negotiated/paid for an extensive warranty contract with Easy Care) because this next bit is a doozy. The sunroof cost was $8,000. However, easy care covered that cost - minus deductible.