Wait, you are also having this problem? 
When you use Simple Last.fm Scrobbler, by chance are you also scrobbling to Last.fm at the same time?
I use Pano Scrobbler and have the same issue, but it’s super weird because my duplicated track is a song I never listened to on my phone. It’s one I listened to from Spotify Desktop and scrobbled with mpris-scrobbler. I meant to file a GitHub issue against Pano Scrobbler, but now seeing this thread, it’s made me double confused.