duplicates in playlist

[Simonline7]

Hi,

So I have this one playlist of >1600 songs. It's like my music library and I consider these to be the my favorite of all time. But sometimes im not quite sure which songs are included in the list when I stumble upon a lost classic.

Up untill about a month ago I would always get a warning message when I tried to add a song for the second time (duplicate). But it seems like Spotify can either not recognize duplicate songs anymore (which would be strange because they probably have some unique identifier) or something else is going on like changes in the warning system. Any ideas?

Thanks, Simon