Model 3 thunk noise in rear

[AlasCon]

Anyone have any idea what this noise is? I just spent hours at the San Rafael Service Center, second time and they can't find anything. I'd kept a spreadsheet for weeks detailing what and when, and even managed to do a sound recording. The challenge for them is that it's occasional, they can't reproduce it. The thunk sounds as if originating in the rear, left, near the charging port but noises in cars are notoriously hard to pinpoint. It occurs occasionally, driving slow, turning left or right, sometime fast and straight, almost always smooth roads, different temps, different SOCs. But I can't reproduce it reliably. I've emptied the trunk, folded the seats down to check hinges, pounded the floor and it's driving me nuts. I'm going back to San Rafael SC next week and we'll swap cars for a week but, I'm hoping someone in the Community has experienced this too?
Tesla Model 3 thunk noise - Clyp

 

[lynnpt2001]

I have the same thing just started 14 k miles....

 

[BayBulk]

That’s a strange noise..I had noise coming from the back of my M3 and it ended up being the trunk. They replaced the cover (the plastic piece that you use your hand to pull the trunk closed) on the trunk and it solved the issue. Also my passenger seatbelt female part rattled. Neither really sounded like that clip. It’s very frustrating to replicate the sounds for the service center and I found the San Rafael department to be very unhelpful. Have you tried using a tone generator? It can help locate noises.

Online Tone Generator - generate pure tones of any frequency