I use the "create similar playlist" function often. Every time I do, there are duplicates of songs in the playlist. Typically only one or two songs will be in the playlist twice, but this most recent time I had one song appear in the playlist SIX times, and four songs appeared twice. In each case, they weren't different versions or recordings of the same song, they're all from the same album with the same URIs. This issue seems to be escalating.