It’s been over three months since Samsung issued the first official Galaxy Note 7 recall, but the company still hasn’t revealed what caused the handsets’ battery to overheat and go up in flames. However, thanks to a third-party report, we may finally have solved the mystery once and for all.

A group of hardware engineers with manufacturing technology company Instrumental took apart one of the few Note 7s still floating around to get to the bottom of the issue. They discovered that the explosive nature of the phone was due to a "fundamental problem with the design,” concluding that Samsung must have suspected this “super aggressive" design was a risk, but went ahead with it anyway as the company wanted an edge over its competitors.

During the first recall, Samsung blamed the problem on a faulty battery. Not long after, the company permanently ended production of the Note 7 and recalled the replacement handsets after they also started overheating and catching fire.

"If it was only a battery part issue and could have been salvaged by a re-spin of the battery, why cancel the product line and cede several quarters of revenue to competitors?” asked Instrumental’s Anna Shedletsky.

It seems the issue wasn’t to do with the battery itself, but the way it had been jammed inside the casing. It was so tightly packed that pressure from natural swelling and stress placed on the Note 7 body was damaging the battery’s separator layers that keep the positive and negative layers apart.

“That pressure could be enough to squeeze the thin polymer separator to a point where the positive and negative layers can touch, causing the battery to explode,” writes Shedletsky.

The report notes that battery swell requires there to be a ceiling above a battery, roughly equivalent to 10 percent of its size to allow expansion into the space. From that equation, the Note 7 should have had a 0.5mm ceiling; instead, it had none.

So why did Samsung design the Note 7 this way? Simply because it wanted to make a smartphone that was super thin and sleek while being incredibly powerful with a long battery life. It appears the company just pushed too hard at the boundaries of what was possible without compromising users’ safety. Every industry needs some risky innovation but, as Samsung will tell you, when it all goes wrong you can lose your customers' trust and be left with a $20 billion bill.