I am having problems with shuffle. I have 2413 songs in my "Songs" playlist. I have the playlist downloaded. I notice that frequently it plays songs from the same artist several times in a row. It is not rare that I get 2-3 songs from the same artist in a row. Last time this happened it was from an artist that has about 20 songs on my "Songs" playlist.

I am not an expert at random/shuffle but the probability of 20/2413 happening 3 times in a row should be low. The fact that it has happened several times suggest that either:

1) The shuffle function doesn't shuffle.

2) Just a subset of the songs are downloaded to the device(even though it says all of them are downloaded) and it shuffles through a way smaller amount of tracks than stated(2413).

3) Something else...

I have tried this on iPhone 6, iPhone 6S, iPad and I keep getting the same results. Is this intended? If so then for what purpose? 

Thanks