To those who've only played with Yonex strings, I don't think you've yet to experience this, since I personally never felt this from Yonex strings before and I've had several dozen string jobs from them. But after trying various other company strings like Gosen, Victor, Ashaway, I noticed that there may be a possibility that a string can snap internally while looking perfectly normal externally. What I mean is after a hard smash, there's a huge snap sound followed by the familiar fuzzy vibration that you get when a string breaks. I look at the racket after the rally, obviously expecting a broken string, but I look to see a perfectly fine string bed still attached to my racket. Puzzled, I play on and the racket plays fine for the most part, but I notice that when you hit a certain part of the sweetspot, the racket feels numb, powerless and non-responsive, like the feel you get when playing with a racket with broken strings. If this was a one time experience I wouldn't even bring it up, but I've had this scenario multiple times, and each time I ask my friend to try my racket to see if I'm not going crazy, and they tell me the racket feels dead as well to them. Is this just my personal experience? Can a string really break internally while looking normal on the outside?
If a string is braided (i.e. composed of multiple strands twisted together like a rope), it may be possible to snap some strands and not others. This is different to simply wearing out the strings from outside in. I don't know if there are actually strings that comprise of a single filament core with other strands braided on the outside of the core, but if they do exist, then I'm guessing it is possible.
Almost all modern strings are composed of multifilament core and then a protective outer layer. The outer layer is for protection only and the main tension is held by the core. Usually the outer layer wears out over time due to string rubbing against the shuttle and against other strings, and when that happens, the inner core eventually wear out too and the string snaps. There is a delicate balance to how much material / cross section area for the outer layer vs inner core. Too little outer layer then it will be premature wear into the inner core, and the opposite is too little inner core it might snap due to high tension/impact. Seems like the latter is what happened to your strings.
