Fill styles break when inserting an instance into a new file?

Hello there,
When a designer inserts an instance from the library into a new design file, the styles sometimes get corrupted (but the same styles work fine on other components).

We’ve tried relinking the colors in the library → republishing → updating the new design files, but the colors are still in HEX, which means the styles are not successfully applied (figma.currentPage.selection[0].fillStyleId is empty).
This is frustrating, any help would be much appreciated (=•́ܫ•̀=)

@Polly Is the Char/Base/Stillness style accessible in the working file? Can you apply that style to any object?