Correct me if I'm wrong, so far these have all been happening on phones that have been used over two months. Mostly happening to phones over four to five months old.
Has this happened to anyone that has set charging limits (80 or 90 percent)?
I'm trying to pinpoint the issue to battery swell which I have experienced all too often with laptops. Hence, they are supposed to be designed to make some room to allow them to swell a little. If this wasn't taken into consideration, cables, chassis and mobo are going to get stretched. If something doesn't fail in a short time, but over a few months, then it is unlikely to be BIOS or firmware issue. I may be wrong, though.