trace through every wire from connector to the other end, make sure theres no exposed sections,
look at every connector at the panel end, is a bit of solder maybe overlapping anywhere?
look inside the connectors as much as you can, is anything stuck in there or a contact bent?
if nothing is immediately apparent, a multimeter could help, other than that contact T.T.'s customer desk and see if they'll Rma you a new one (Header,not case)
sorry I cant be more helpful than that man