CT Corvette

Hello - just bought my first corvette (used 2017 with 3k miles). Ive wanted one for my entire life and was finally at the point where I could buy a slightly used 2017 C7 LT1 base model. I absolutely love the car...but it is breaking my heart. After a week of driving, the I noticed a somewhat loud metallic clicking sound coming from the rear hatch area. It is coming from TWO places (near the rear corners) and happens when riding over bumps at any speed. I consider myself handy with cars so I immediately starting trouble shooting after searching possible causes online and also on this forum. As of a week ago and after many hours of inspecting, I have ruled out the most commonly discussed problems such as; speakers, torque screws in body panels, loose interior molding clips (including the small side window panel), exhaust heat shield, hatch door rubber height adjusters, hatch door struts, targa top fittings, etc. I even removed the rear body panel to see if something was loose. I don't give up easy, but man - I cannot figure it out. With that, I decided to bring it to the local Chevrolet dealer last week. Well, its now been there for 10 days and after many hours of their own diagnostics and all interior and exterior panels and body parts removed, they cant figure out what is causing the clicking noise either. My C7 is now basically only a frame - completely taken apart. Ugg! As of yesterday, they told me that they have called in an out of state "Regional Chevrolet Engineer" to help and he will be arriving in a few days to perform his diagnosis. With all of this, Im wondering if there are any other ideas or suggestions that this forum can offer?