I don't know how to fix it per se, but I've noticed that those plugs are very, very tight to the wall - had trouble even getting one into the socket the first time.

The cable will have to be returned for repair.  This is a great example of how not to remove a cable from its jack, or in this case, receptacle.  It doesn't matter if it's a power cord, or an interconnect or speaker cable you should never grab the cable and pull.  Always and only grab the connector and pull on it.

You can probably imagine this practice has been going on since hi-end cables were invented.  How many RCA cables do you think have stretched strands at the contact points, broken strands and or loose contacts?  Something like that which can't be seen can instantly undo any sonic benefit the fancy wire may have had and still manage to operate so that the user has no idea anything has happened.

No worries, we can fix it. : )