Hissing from one of the two NT5 mikes

Question

In a laptop recording stereo setup one of my two NT5 stereo microphones has a strong continuous hiss that will not go away. It hissed the 1st time I used (2 months ago); but went away when I returned it to the store where it did not hiss and I have subsequently have been able to record with it. Now the hiss has returned. I have tried swapping the microphones between the cable and the hiss moves with the microphone. Any suggestions?Crossrich