Kudos to DR and their fantastic customer service. The problem you encountered is caused by the winding being loose in a spot - not being wrapped tightly over the core. It is indeed possible you got a defective string - they are handwound, after all. However, it is also possible you damaged the string yourself during installation. You should put a 90 degree bend in the string at the proper location (about 3-1/2" to 4" past the tuning post) before you cut it, then cut it about 3/4" past the bend so the short bent end fits down into the hole in the post correctly. Also, do not wrap the string around the stationary post by hand. Start with no winds on the post and then take up the slack by turning the tuning key to create the wraps. Following these techniques will minimize the possibility of the windings loosening up on the core and creating the chorus-like sound.