[chris11]

I think it's both contact and wire resistance.

It is technically possible to solder a new connector on. LTT did that in a video. https://www.youtube.com/watch?v=WzwrLLg1RR4

[ryao]

Uneven abnormal contact resistance is what causes the wires to become unbalanced, and then the remaining ones whose contacts have low resistance have huge currents pushed through them, causing them to overheat due to wire resistance. I am not sure if it is possible to have perfect contact resistance in all systems.