It seems, that len(self.__random_files) - 1) always has only
2 digits. I have emailed you this. I have to setup my SDK
again to debug this.

Edit:
I have got my SDK running again. I added a
print len(self.__random_files) - 1
to the code.
It starts always with 60. If I play other contend, and readd
the playlist again, then the values are correct (more than 1000).
Something lets the list decrease to only 60 items.