I used to have this happen randomly with many brands of strings. this is my "theory" and remember this is just a theory. I think that as the core wire is stretched under tension the overall diameter of the core shrinks while the wrap stays a constant. since the wrap is not under direct tension it loosens its grip. this causes the wraps to loosen around the core wire and deadens the vibrations. most wire is made simply by stretching a larger diameter spool of wire until it reaches the desired thickness. since steel isn't always perfect some sections stretch faster and under less tension than others. so the more you bend, tune and play the thinner the core gets over time. I went trough the same thought process as you and after long hours of research in wire production and steel construction, this is the most logical explanation i could come up with

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I find that sad. I am always trying to learn new things and I find I learn better by asking "why" instead of "just get(ting) on with life".

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Bill

Intersting theory. Thanks.

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Bill