Yeah, I'd expect it to be something in the power delivery circuit. A bad cap or regulator. I've successfully replaced various components like regulators and chokes on cards in the past... But its a lot lower success rate than just reflowing an artifacting card.

The problem with modern cards is they're so darn complex. You can take a multimeter and do diode checks or hook various circuits up to an oscilloscope... but its a needle in a hay stack.