24w33a added new sounds for spawners, including step sounds when walking on it. However, in sounds.json the subtitle for it is bound to translation key subtitles.block.generic.step instead of the usual subtitles.block.generic.footsteps. As the former key doesn't exist in language files, the subtitle now shows as untranslated key, which I assume is not intended.

Steps to reproduce
 

1. In Accessibility settings, turn on subtitles
2. Place several spawners, and walk on them
3. Note that subtitles.block.generic.footsteps can occur instead of "Footsteps" or its translated variant

Or just inspect the sounds.json built in.