If a sound is played then stopped while still playing, the subtitle appears and slowly fades away as if the sound is still audible.

Steps to reproduce:

1. Enable subtitles in Options -> Music & Sounds -> Show Subtitles: ON
2. Run command: /playsound minecraft:entity.enderman.scream master @s
3. While the previous sound is still audible, quickly run: /stopsound @s

Notice the sound cuts off, but the subtitle "Enderman screams" remains.