Some songs missing from some artists

I'm not sure exactly what the cause of this problem is, but it seems some songs that scrobble properly with the Web Scrobbler plugin do not scrobble onto Rocksky. Some example tracks I've found that do this are "On & On" by M.O and "Choose Sides" by them and AJ Tracey. I am unsure why exactly this is the case, I wasn't sure if it was because MusicBrainz lacks some album art for some of their songs as they're small artists but after uploading some and having it approved, it's still not working. If I notice it with more tracks, be it from them or other artists, I'll be happy to let you know if it may help troubleshoot.