I think the problem in these Android phones that are catching fire may be the fast charging technology. Pushing large amounts of wattage through a port that was never intended to handle it, into a battery system also not intended to charge so rapidly, is a formula for disaster in the long run. The batteries charging so rapidly physically expand as they heat up while receiving the charge. . . then they cool down and contract when the charging is completed or after they've received the rapid cycle and go on to the slower, trickle charge to complete the full charge. This heat/cool, expand/contract cycle leads to internal damage. In addition, larger power densities passing through a power port not originally designed to handle the load will also cause the traces and wires in the port to heat and change physical characteristics. The connection is physical, and arcing can occur at higher density loads.
The normal, expected rate of Lithium Ion failure rate is 1 per 10,000,000 per year, but that is in normal trickle charged cell batteries. I have not seen any data collected on batteries whose cells were rapid charged. Making the assumption that the normal rate would be the same for rapid charged batteries, especially ones that undergo multiple rapid charges, would be foolish. . . but apparently that is what they are doing.
The Motorola Turbos are such rapid charging phones as was the Samsung Galaxy Note 7.
Apple, which certainly could include rapid charging in their phones as the technology is simple and cheap, has chosen NOT to include such a capability in any of their products for apparently good reasons known to them. Perhaps Apple research did do the rapid charge failure testing?
Without question her Android the port overheated due to excessive current since there was no short circuit. Heat is the enemy of all things electronic, including batteries.
What is sad is that EE graduates rarely understand these issues even though it is a part the curriculum. “Excessive current overheating a circuit? Nah, it’s only a wire.” Changes are these days it wasn’t even an EE that made the decisions and some BA bimbo with a PMP was the project manager.