This happens at stock clocks after moving tdp over 100 which immediately triggers it. I haven't even tried over locking it yet. I am debating on sending them back for a.different model as even if I use a different psu its stressing the connector more.then it should. Having seen melted connectorrs with my 290s while mining scrypt (psus fault) its a good idea to errr on caution. This applies.to.750s as well.
Tldr more power connectors the better.
The card is rated at 145W, the 8 pin can handle 150 plus 75 from the slot. I don't think the problem is the
connectors. I'm also not sure about an over-volt fault. If the card is drawing too much power it would
cause a volatge drop. An over-volt might be the PSU or the mains. If you're confident about the power
send the card back.