Problems

One side of the earphones provides lower volume than the other.

 

Solution:

 

Earphones have a protective mesh, just in front of the driver units. In time, that metal mesh can be blocked with earwax and dust and it can dramatically reduce the volume level of the earphone. When it is completely blocked, it is almost impossible to clean it. It is best to keep clean the earphones and keep them in the protective case/pouch when it is not in use.