alt Hacker NewsI’ve had this failure on soft-touch usb cables from the 2000’s, not related to movement, just in a box in room temperature storage they disintegrate like this. It was described to me as thermoplastic elastometer degradation but I’m not really satisfied with that vague of an answer. Main comment thread when I first jumped in to discuss it: https://news.ycombinator.com/item?id=28054090
I have a couple of USB cables from the 2000's like this, some of them original apple cables. But most are fine.
While some show brittleless, more plstics goes gooey and tarry - especially some ABS coating that makes the material more grippable,like computer mice or binoculars.