I just bought a used 2015 Model S 85D, the car looks and feels new as it was a one-owner well taken-care of car. However, only four speakers work currently. It sounds like I have a kid's radio in the car. It is equipped with the ultra-high fidelity sound package which is supposed to have 11 speakers and a subwoofer. The speakers are there, but they don't work. Tesla sent a software update but it didn't fix anything, and neither does rebooting the computer. I had an appointment with Tesla on May 2nd but they postponed it to May 8th to "get the parts" needed to fix it. The former owner told me that the sound went out after some sort of infotainment update. So I keep thinking it is software related but Tesla is going to replace one of the amplifiers for over $1000. Any thoughts on this for anyone having had this issue?