constant problems with audio downloads in app

for the last two month or so I constantly have problems with the audio download in the app.

It downloads the lesson audio but (which means thre green circle is full after the blue "lesson"-box but when I want to listen to the whole lesson the audio stops after some minute and jumps back to zero.

Last example of this was the "baba and erzi snake"-lesson.

Can this please be fixed soon?

It is really!!! annoying!