[Majromax]

> But the new connector is still only rated for 600W (if used within spec),

I think that's the problem right there: running the connection at its rated limit. It implies that a damaged or slightly out-of-spec connector could fail, as we see happened here.

Defensive engineering involves safety margins for safety-relevant specifications. Running a digital signal at the limits of its specification is one thing; data corruption is a detectable problem and not inherently unsafe. Running power connections at rated limits is something else entirely because the failure modes are physical damage, fire, and electrical arcing.

600W of power delivery is no joke, and I'd like to see that power carried over cabling and connectors with absolute maximum ratings much greater than that, say 1kW. Per the specs, it seems that each of the 12 current-carrying conductors in the connector runs about 9A. A dodgy connection that results in just 1-ohm of resistance would then represent 80W lost as heat at that point.

Frankly, I think that running 600W over a single 12V multi-core cable is insane. You're talking 50A of current, or about the same current rating as the largest typical home circuits for an electric kitchen appliance or car charger. In the home, that calls for thick structural cabling, but it appears (https://www.cable-sleeving.com/pcie5-12vhpwr-16pin-connector) that the in-case recommendations are to use 16AWG wire or even a touch thinner.

[arghwhat]

The power pins are in the spec rated for 9.2A each, for a total of 662.4W@12V. To be compliant the connector must handle at least that. At the same time, the max advertised capacity is 600W, so a device must pull at most that.

So by the spec it must have at 10% headroom - and to live up to that, manufacturers must add their own margin on top. Rating for 1kW would be a 66% margin and a humongous waste of copper, and it wouldn't solve this contact issue in the first place.

Regarding wire gauge - unrelated to the problem at hand - 16AWG is already overkill. For house installation in EU, we rate that gauge for 13A to 18.5A depending on thermal conditons, with 13A being "very poor" thermal conditions (no cooling and surrounded by other hot things). With 6 pairs in parallel, that gives a conservative minimum of 78A capacity - and with the excellent thermal conditions of a case with fans ("very good" is normally just a dangling cable, not one with fans cooling it), the realistic capacity should exceed 120A. As you say, we need only 50A, so that's a 140% margin! Even 20AWG would be plenty here.