Add me to the list of folks for whom this thread helped.
First speaker failure in my 2013 Model S happened a few years ago. Didn't find anything online back then about the problem, wound up just buying a new replacement from Tesla, installed it myself. But then after we got the car back from the shop last year, all three of the other door speakers had stopped working too! In hindsight, I don't see how the work that had been done on the car could've been related or caused the additional failures; probably just coincidence. But of course at the time I was skeptical.
Anyway, I've lived with the bad audio for almost a year now, too busy to deal with it myself and not wanting to spend an arm and a leg at the Tesla service center to have them fix what I wasn't sure wasn't their fault in the first place.
I'm glad I procrastinated, because now this thread is online and someone else did the hard part of figuring out exactly where the fault was.
For what it's worth, the melted plastic on the speaker frame, looks to me as though it's done intentionally during manufacturing as a way of pinning the speaker leads down. Based on the failure, I'd guess the manufacturing process is sloppy and overheats the spot on the lead where the plastic is melted, weakening it, causing it to eventually fail. Or possibly it breaks the lead at that time, but it's still held (barely) together by the plastic. Either way, I guess vibration over time causes the break to be complete and the speaker stops working.
I've already fixed one of the speakers (wanted to verify I had the same problem with the same fix before tearing into the other doors), and am happy to report that soldering a jumper onto the leads to fix the break worked perfectly. I'd verified the break before doing the work, just one of the leads had the break but I figure I can't really trust the other one, so I added a jumper to the other one, and will do that to the remaining two speakers that still don't work.
Thanks again for everyone else who shared their experience, and of course especially to
DABESQ2 who originally reported the fix.
Of course, I am irritated, to say the least, by the manufacturing process Tesla's using (or rather, their lowest-bid supplier is using), and the fact that in spite of that it's obvious lots of people are experiencing the exact same failure, they are hiding behind warranty limits and not stepping up to correct the problem. I admit, that kind of approach is far from unique to Tesla. But for what these cars cost, I'd expect better customer support than that. But at least the owner community is helping fill that void.