Ive gotta say that as an Electrician, the thought of conductors breaking inside flexible cords like that is puzzling and kind of makes me scratch my head. They just don't just sever and break, that easily. Both CU and AL conductors should have no problem bending and flexing as they are soft metals that are stranded and are protected by a flexible thermoplastic jacket. I find the severed wire in the flexible cord theory to be very odd but I suppose its possible with manufacturing defects.
As far as trying to pinpoint a common thing we might be doing that causes the failures, I found it interesting he mentioned not over tightening the cord grip connectors. They felt a bit loose to me when I got my unit so I gave them a little turn until it felt "snug" but not tight, and certainly not tight enough that it should cause the wire to sever. I also rattled the handle twice briefly to demonstrate the presence of the balls in the injector to a friend, but again the handle is designed to be moved and should have no issue handling some brief shaking.
Waiting to see what happens with my unit, it is at Oldhead getting fixed. Not too thrilled to see the new cords being used to repair, the shrink wrap looks hacky and detracts from what is supposed to be a very aesthetically pleasing TED. Maybe its just me being anal because making electrical work look good is my job. At any rate, if it is the permanent fix ill be satisfied.