This never used to be a problem -- physical sales were easy to apportion, and the iTunes model was similarly simple. With global streaming services, it can take a while to work out who to pay, and some royalties end up in limbo. Spotify is quick to note that less than one percent of the $3 billion or so it's doled out over the past 6 years hasn't found its way to artists, but anything above zero isn't great. So, how's it going to fix things? Money!
"Today we are excited to announce that Spotify will invest in the resources and technical expertise to build a comprehensive publishing administration system to solve this problem." -- Spotify
The quote above is about all Spotify has to say on the matter today. It's committing to invest in a solution, and says it'll work alongside industry bodies like the National Music Publishers Association to "fix the global problem of bad publishing data once and for all." The exact timing of this announcement is quite clearly a response to the recent spate of bad press the streaming service has gotten, but if it ends up with a better solution for artists, then who cares?