Also covered by CNN:
https://edition.cnn.com/2018/07/12/a...ntl/index.html
Citing unnamed industry sources, multiple Chinese state media outlets reported the cockpit crew were smoking in violation of aviation regulations, and caused the loss of cabin pressure and drop in altitude when they mistook two switches as air recycling fans and turned them off.
I'm much less concerned about the smoking in the cockpit and more concerned that they appeared to be pushing buttons randomly to find out what they do!