Full black style turns into transparent in one specific file

I have a main library with a token system and styles generated. All the other files are connected to this library and they have access to the styles.

There’s one specific file where the black border style started showing as transparent. It was working until yesterday afternoon, but out of nothing it stopped working. When I open the styles edit mode, it shows the preview as transparent and no property at all (like if the style was empty/broken).

There’s a lot of people accessing this file, but as the style is coming from a linked library, nobody can edit it.

The style is still working in the library itself (tokens are correct) AND in all the other files.

Does anyone know what could be happening and how to solve this issue?