Question about Beyerdynamic MMX 300 2nd Gen.

Does anyone else have the following problem: - Headset works perfectly, as does the microphone. - However, when I "mute" the headset on the cable, participants in a call hear my sound, i.e. what is being played back. When it is not muted, everything is fine. Very strange, looks like some kind of loose contact, but wanted to see if anyone else has the same problem.