Check the pins and connectors. Physically inspect them. Occasionally it happens where the barb on the pin doesn't grab the connector, the connector is gouged or the barb has pushed in too far. When that happens, you plug the connector into the gpu and it looks fully seated and correct, but that one bad pin gets pushed backwards. Instead of that female fully surrounding the male gpu pin, it just sits tip-tip, which can/does create heat/spark under higher loads.
If the plastic is warped or melted, suggest replacement or at a minimum fixing the pin so it no longer pushes back out when seating.