song disappearances

songs that i will have listened to for a while will randomly disappear from my stats presumably because a song by a similar name of the same artist becomes the main one you track under? but anyway, for example my third most listened to song ever (this corrosion - [the] sisters of mercy)has vanished, which i find a bit disappointing. this happens with lots of other songs i love too but it seems weird to pay to track just for your top songs to be randomly removed