My 'Favorite Songs' library is not synced across all devices.

When I add songs to my favourites on my iPad, they sometimes do not show up un my iPhone. However, when I add songs on my iPhone, they all come up on my iPad. I also have a Windows Laptop where I use the  Spotify app sometimes and the situation is similar to my iPad; all the songs show up there.

According to my laptop, I have 3,157 songs on my favourites list but on my phone, only 2,645 show up. 

I have tried uninstalling and reinstalling Spotify on my phone but nothing changed. Is there a way to solve this?

I am also currently a Free user though I don't see how that should matter.