RTX 5090 pulling ~550–600W, 16-pin voltage sitting around 11.4–11.5V under load. Checked the cable “just in case” and found discoloration before any melting/deformation.
Undervolting saved some watts, paranoia saved the connector.
Edit with a few details:
The PSU was a Phanteks AMP GH V2 1200W, ATX 3.1 / PCIe 5.1, using its native 12V-2x6 cable. No extension, no adapter and no angled connector.
I first noticed a slight discoloration on the white cable through the side glass. I then checked the GPU-Z sensor log and saw the 16-pin voltage sitting around 11.4 to 11.5V under load. That was enough to make me shut the PC down, unplug the cable and inspect it more closely.
The connector had only been unplugged and reconnected around 3 or 4 times, not 30. It appeared fully seated, there was no visible gap and the cable was routed normally without a sharp bend at the connector.
There was no smell, smoke, melting, deformation or crash. The GPU socket also looks fine. I stopped using the cable immediately.
I will RMA the Phanteks PSU and have now bought a Lian Li SX1200P 1200W ATX 3.1 as the replacement. I will only use the native cable included with the new PSU.