The statement was translated from its original Chinese by The Next Web:
“We found that a small number of iPhone 6s devices made in September and October 2015 contained a battery component that was exposed to controlled ambient air longer than it should have been before being assembled into battery packs. As a result, these batteries degrade faster than a normal battery and cause unexpected shutdowns to occur. It’s important to note, this is not a safety issue.”
The release continues, saying that “outside the affected batch, a small number of customers reported an unexpected shutdown." Fortunately, the issue isn’t a safety concern, and will likely be sussed out through a new diagnostic feature to be rolled out during next week’s iOS update.