I was about to post something similar but you already found something with more details. The resistance between the male and female connectors can be much high

I was about to post something similar but you already found something with more details. The resistance between the male and female connectors can be much higher than what most of us have expected. While I was down the rabbit hole trying to power one of my SBC correctly, one of the findings was that the resistance introduced by the connector can go up to *0.5 ohm*(don't even mention those dodgy power supplies and cables). But even if the resistance is only 0.1 ohm, it's still a big problem as the current is for sure above 10A for a single pin, and then the heat dissipation will be over 10W, which will of course concentrated around the contacting point, which is close to the tip. This explains why the tip side was melting.