As Freso mentioned on MBS-4782, https://beta.musicbrainz.org/release/fd90a61b-c16c-4d68-b8aa-945bf0569882/cover-art is not showing the cover art since the release was merged. Ollie said he'd told the indexer to retry all failed events, but it still doesn't work.

Since then, two more releases which were merged have broken images:
https://beta.musicbrainz.org/release/e6d3600e-c847-3ffb-b2a2-dec1f3c2b172/cover-art
https://beta.musicbrainz.org/release/fa657fda-ac14-4e44-a16f-e064ac198b13/cover-art