Sounds like they messed up the connections at either the plug or outlet end of the cord. Now as it happens I have a way to tell which. but it is a product designed for other use (Antenna Analyzer) but the only way I know of to fix the cord is to replace the faulty end. Problem is deciding which end it is.
Oh a multi meter that reads capacitance may do it too
The good end if you measure legs to ground or legs to neutral will have a higher capacitance but I don't know if it will be enough to notice. The bad end the two legs will show different capacitance.