My 2011 JGC did the same thing. It had to do with something in the lower lumbar support mechanism. Since that part moved in my seat, it developed a popping sound when accelerating or decelerating. I thought the seat mount was a problem but it was the lower inside of the seat related to the lumbar mechanism.
Anyway, the dealer totally messed my seat up with the repair. They broke all the hangers and plastic parts that snap on. They wanted me to accept it that way. After multiple tries and trips to that dealer (Tr-County - Heath, Ohio) I went to another dealer. I would never recommend TRI-County Jeep to anyone!!!!!!!!!!!!!! I went to Liberty Jeep, New Albany, Ohio and they were able to eventually kind of fix it. I had the Jeep Customer Care involved and they were useless! The seat popping is fixed and they replaced the hangers in the seat back and the side plastic seat bottom, but there is still one plastic part that keeps popping out and won't stay in. This is because the metal base at the seat bottom is bent and doesn't align properly. Jeep should have replaced the entire seat but wouldn't because it went out of warrant near the beginning of the process. I ended up making 18 trips to the dealer to try and fix this problem, so good luck getting yours fixed!