Are you referring to the wireless headphones which use a standard micro USB connector or the propretary magnetic charging connection on the detector and wireless module that atteacts iron particles from black sand? Because, he's talking about the non-magnetic headphone charging port which really should not be collecting debris unless someone is constantly throwing their headphones in the sand.
Sometimes, the USB connector on the wireless headphones breaks internally (not the most robust design). Definitely contact ML and get a replacement pair under warranty. And if they are heating up, that could be a sign of a lithium battery failure, so stop attempting to charge them or you could start a nasty little fire.
