Odd span stuff in this post. As an old programmer when it comes to random there is nothing wrong if a random number generator doesn't pop up a number for a very long time. It was interesting for a time to discuss what random is as we wrote some apps but at 18 to 19 GB of files you could have hit some limit on the number of titles that will be read in or create the issue you are seeing.

I'm not going to call it a bug but a limitation as very few folk can spend thousands of bucks on that much music. There are pirates that collect such but they usually will never reveal they downloaded it all for free.
Bob