A relative of mine got and returned a Galaxy Note 2 phone because of intermittent stylus problems. The stylus would not work in certain parts of the screen, namely the middle part of the right edge. The Guys at mobile shop where amazingly understanding and replaced the phone when she demoed this problem to them.
What happened is that the new phone had the same issue. The phone was presented to your’s truly and I was very amazed by this. To me samsung was super reliable and two phones in a row is just not bad luck.
So I took a look at the phone and noticed something strange, the area in question that sometimes does not work on the Samsung Galaxy note 2 with the Stylus was directly located on the other side of a magnet in the flip case that she had on her phone. I removed the case and put that same magnet in another area and low and behold that area now had problems and the other area was clear of problems. When we removed the cover totally the intermittent problems no longer came back.
Non Authorised accessories can do harm but I never saw a case do something like that.
Moral of the story, not all defects are really defects, Mobile shop in Egypt really mean business and exchange faulty devices, and they do not have the experience to know what is faulty or not.
But most of all if you have a problem with technology solutions can sometimes amaze you.