The new adapter cable has three 8-pin input connectors that merge into a single 12V-2x6 connector on ... overheated up to 150C on some wires due to uneven power distribution on all cables.

The 12VHPWR connector (and its 12V-2x6 successor) is notorious for their vulnerability to high temperatures on power-hungry GPUs, to the point where it can melt. To combat this on the adapter side ...