Samsung's Note 7 woes boil down to "irregularly sized" batteries and manufacturing issues, according to The Wall Street Journal.
The report comes two days before Samsung is set to hold a press conference where it will formally announce the findings of its investigation into the fires and explosions that prompted its Note 7 recall last year. The Journal on Friday reported that Samsung's investigation revealed that "some batteries were irregularly sized, causing overheating, while others had manufacturing problems."
According to the report, Note 7 batteries came from two suppliers — Samsung SDI, one of the Korean tech giant's affiliates, and Hong Kong-based Amperex Technology. When the handsets first started catching fire and blowing up, Samsung found that the batteries made by its affiliate were to blame. The company recalled these handsets and increased production of models with the Amperex Technology batteries.
The rest of the story has been well documented: The Note 7 returned to store shelves in late September but it wasn't long before the replacement units started catching fire, too. Samsung eventually ended production of the device in early October and asked carriers to halt sales.
Citing unnamed sources, the Journal reported that the batteries from Samsung SDI "didn't fit properly in the phone," causing them to overheat. The flaw affecting replacement units was deemed the result of a "manufacturing issue resulting from the quick ramp-up in production." Details of the manufacturing issue have not been made public.
Samsung has since come up with a multi-step testing process for future products, the Journal reported.