There are alot of problems with play queue and the list, that shows following songs and especially in suffle mode. Following observations are made using a premium account on Sony Experia Z1.
When an album or playlist is played in suffle, the following songs -list contains often duplicate songs (same song can repeat many many times) and all songs can't even be found from the list... I mean, seriously broken.
What comes to adding songs in the play queue, it's just as bad. Worst case is when you add a partially saved album from Your Music to the queue - after this the queue may contain duplicates, be incomplete and it may contain songs, that weren't saved in library but which are on the complete album. Funniest thing is that as the queue is scrolled up and down, it changes spontaneously! What is this?? Also removing songs from the queue doesn't work reliably, marked songs may stay in the list even after trying to remove them from it. IDEA: It would also help if there was an easy way to clear the whole queue instead of having to mark each song in the queue separately - one long album is already a pain to remove from the queue.
Finally, I liked the list of following songs when it used to work in a such way, that when you klicked a song in the list, songs before the selected song would be skipped even in suffle mode. Well, maybe it should still work like that and I'm talking about another issue? I have used to use this skipping function to limit the playtime of a selected playlist or album, as there is no sleeptimer. IDEA: I think there should be a sleeptimer.
Now, this is a serious pack of problems and I wonder how it is possible that they exist... Maybe these problems are limited only to my device, meaning that my Spotify has gone corrupted or something and I need to reinstall it - again! Maybe I'll try that next.