Problems with AX760

Hello,
after scouring the internet for an authoritative source on PSUs I've found this place where people seem to know their PSUs. I hope you can help me solve a problem.

Around April 2013 I've bought an AX760 that has been working great until the last two months, were when playing games the computer would restart. The card it was powering at the time was a 780ti Superclocked. I got the card replaced with a 980 and, with this card the system would just crash as soon as I started anything 3d.

I tried just about anything, until on a forum, someone suggested to swap the 1 to 2 pci-e cable I was using for powering the graphic card to 2 single pci-e cables. However, as I tried to unplug the cable, it didn't budge. It took a great deal of strength to get the cable out. When I managed, I noticed that one of the pins had its casing melted.


http://ift.tt/1JW8v5w

What was left of the casing, had melted inside the connector with the result that it was impossible to utilize it anymore.

http://ift.tt/1fqoChV

Using the other connectors, the PSU works as it ever did, there aren't crashes anymore under 3d load and the system seems as stable as ever.

I've got a couple questions:

• What could have happened? I never overclocked the 780ti that was connected to the cable (factory overclock notwithstanding)
  
• Is it safe to keep using the PSU?

Problems with AX760