Patterns: Broken preview (no styles)

Are you referring to the previews on the editor or in the admin list page?
And are those patterns have the proper style when added to the editor's content?

You need to make sure that the frontend style used by those patterns are being "injected" into the editor.
For the patterns list admin page, it's not supported yet but you could inject/add the pattern style using preprocess hook for that page.

Fixed the issue by adding { preprocess: false, attributes: { id: ---- } } to the css asset in the library.

Thank you!