Hey I posted about this before but got no response and it was locked. This problem has had a pretty decent impact on my stream so being able to fix it or just get an acknowledgement that this post has been seen would be awesome.
Essentially, AutoDJ does not actually source from the entire Playlist, it seems it sources mostly from the top/most recent 100 or so + a few random ones from other parts of the playlist. That means refreshing several times will produce similar songs being queued, and until the playlist is majorly updated, you'll hear the same songs repeatedly.