The first is that the number of new subscription notices rarely ever matches up with the actual new wallpapers in subscriptions count as seen here:

This is usually the case when one wallpaper matches multiple tags I'm subscribed to like redhead and Cintia Dicker, for example, so I'm not sure if this is a bug or a design flaw. Either way this is fairly minor.
The second and more majorly annoying bug occurs when you have multiple pages of new wallpapers on the main subscriptions page. The wallpapers you see on one page can show up again when you go to another page there by making it almost impossible to know if you've actually seen all the new wallpapers. Here's a funny case of the same 3 wallpapers showing up in exactly the same order:


