@msrex I checked this now. I see that there is a bug, not updating the song when disc is changed, but I see it's correctly updating when title and track is changed.
But I don't know if that bug could explain what you saw happening, it could happen if the song was ripped while strawberry was running, and disc was updated after the song was initially read from disc.
If you manually tagged the disc later, or the ripping program tagged it later.
If you see way to still reproduce the bug without updating the disc, I'd like to know so I can fix it.