The left ear cup can become decoupled from the post (see photos).  It tends to stay on when they are worn, but if the earcups are flopping around it can separate.

They do pass sound.  The right sounds like a normal volume, and the left earcup volume is diminished.  Fiddling with the plug can make them both sound fine, intermittently.  May be repairable. 

Sold as-is.  Will ship in a box to protect the original box.

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