I noticed a lot of songs in my collection have this very strange line which is only visible when in the spectral view. The only way I’ve found which removes it is by applying a high-pass effect which cuts off anything below 5 hz. That fixes it!
You may ask: Why fix it? Well, it causes an audible pop sound when it reaches the end of the song and stops. It is very odd!
Yes, that helped me pinpoint what causes it: I am normalizing tracks (so when I export to mp3 it doesn’t distort) and it actually adds that to the track if I have it remove the DC offset as well, whereas if I normalize it without removing the offset it doesn’t cause that issue!