Was there a new "feature" rolled out that allows playlist creators to override the local crossfade settings? I'm noticing sporadic, platform independent (iOS, FireTV, Windows) playlists which include 5 or 10 second crossfades.
Some playlists feature special cross-fading/mixing done by Spotify or artists. If you'd like to use your own cross-fade preferences, I recommend creating a new playlist and dragging all songs from the original playlist to your new playlist. That should help. Let me know if you have any questions.