The subtitles subtitles.block.shulker_box.open and subtitles.block.shulker_box.close have an inaccurate translation for English (US), they say "Shulker opens" / "Shulker closes" instead of "Shulker box ...".
/playsound minecraft:block.shulker_box.open master @s
/playsound minecraft:block.shulker_box.close master @s
The subtitles say "Shulker ..."
Wrong subtitles caused by missing distinction