Khan Academy - e.g. Music

When I first used the App, all was perfect, then later on during further uses the pictures (specifically, Brahms Academic Festival Overture) became blotched and smeared, thus unrecognizable. This is a great App, but it has to be rectified, or else it is useless. I will wait for its revision otherwise I will cancel it.
Thank you....... Hid

HNG-Hid about Khan Academy, v3.1.12