I have a share button in the Spotify app I’m developing. I’m using the exact html supplied in the developer guidelines ‘buttons’ section, and I have also imported the standard CSS files.
My button renders with the icon missaligned (too low), e.g.

I notice this also occurs in other Spotify apps, e.g. Pitchfork

In native Spotify pages the icon is positioned correctly, e.g.

Is this a bug in the standard Spotify’s app CSS, or is it a problem with my app?
This is definitely a problem with Spotify’s CSS. The positioning of the icon is defined at shared.css line 135:
I added the following to my stylesheet to put it back to the right place: