ISNI links with spaces between every four numbers do not work as intended.
For example:
https://bookbrainz.org/author/3fe921c7-1802-4452-89fd-025b803bc36e
The ISNI link leads to https://isni.org/0000%200001%202101%202885/
While with
https://beta.bookbrainz.org/author/057b64ef-66dd-4c90-9828-65f7cfbf58e5
The link leads to http://www.isni.org/0000000121303076 which properly directs you to the database entry