I have an Honor 5X running LineageOS, and I'm trying to use an external SD card as adoptable storage. After migrating my data, my internal shared storage usage does not go down. Specifically, "Music & audio" shows up as 6.9 GB on both the internal shared storage and the SD card. There's also an unusual "-6.1GB" under "Other" when I look at the storage usage for the SD card.
I don't know if it's relevant, but the "Music" directory is being watched by Syncthing. Is there something I did wrong in setting this up?