Trying to run several hundred amperes through 12 or 14 gauge wire is something that is never going to work reliably. Either nVidia and company are going to have to make their GPUs more efficient or they're going to have to go to a higher voltage, higher gauge wire in such an enclosed space is problematic but so is running that much current through existing 12 or 14 gauge.

BTW, I have similar problems with my i9-10980xe servers, overclocked 18 cores can draw 540 watts full load, the VRMs and the traces on most brands of motherboards will not handle this long term, Gigabyte being a notable exception, the traces on their high end boards are twice as thick as most others and the VRMS have heat pipe cooling with a small fan on the pipe radiator. I've found that running the heaviest gauge power cables I can get AND getting cables that have the wires independent instead of in a ribbon for best heat dissipation, combined with a huge amount of fan to keep a lot of air flow going is essential to keeping these things from melting down or flaming out. I even had an Asrock board melt the solder at the power connection on the CPU socket it got so hot from the current draw.