Watch out for those Y adapters, folks. They often won't take a lot of power either.
Exactly, socket is bad, nothing to do with wire gauge.
That's only one possibility. They're the same type of Mini-Fit Jr connectors used on video cards. It's either poor contact inside the connector, too much current running through too thin wires, or a combination of the two causing things like this.
The higher the current draw, the greater the risk of failure. Absolutely none of my mining cards are overclocked, or even running as high as stock speeds in many cases. I have had zero connector failures on any one of my mining PSUs over the last 3 years because I'm very careful about this stuff. I prefer to give up a little mining profit so I can be absolutely sure nothing starts a fire in that room.
Currently running one Seasonic X-1050, one Corsair AX1500i, one EVGA P2 1600W, one Super Flower Titanium 1600W, and one Thermaltake Titanium 1250W. The Corsair's been running the longest.
The Seasonic is only temporary at the moment, but it's not a newcomer to my farm. It ran 24/7 for a good year on a four card Tahiti machine with no issues because I wouldn't push the cards hard enough to cause issues. Right now it's running a Hawaii (two 18AWG cables), a Tahiti (one cable), and a Pitcairn (one cable). All cards downvolted as far as they'll go with reasonable speed.
I have since switced to server PSU that are rated for 24/7 operation.
That's really the best way to do it.