Hey
@Mansi_ASUS, thanks for your reply.
This definitely has nothing to do with cleaning agents, at least in my case, because I didn't use any. And as shown by FunBike31, I'm not the only one. And you can already find more cases if you search for it.
The problem is not solved by simply replacing it with a new back as long its production quality is the same. It will occur again after a few days. Asus first has to recognize the problem and produce the back more resistant.