I saw this reddit post after purchasing Antec sp1300, I rechecked my pcie cables and saw small shining solder joint at psu end connection of the pcie cable. Removed the cable, pushed the ground cable sticking out slightly and reseated it. Have been using for a year no issue with 1.1-1.2kW load for hours to days.
Would caution anyone purchasing to check all the cables to see they are in place and seated properly before plugging. Antec should improve their QC, apart from that these are seasonic units, very reliable.