Strangely, I was not prevented from adding a duplicate artist-URL relationship.

• www.core22.ch URL edits https://musicbrainz.org/url/9687fe3a-6de8-4d77-ab49-160a332bcd48/edits
• Core22 Artist edits https://musicbrainz.org/artist/5341e657-bcf0-446b-b1b4-ab7b05f8f54a/edits

Core22 was linked to www.core22.ch in 2020: https://musicbrainz.org/edit/71403382
Today I was not prevented from adding same URL (but with end date) in artist edit page: https://musicbrainz.org/edit/135864632

Then, I tried to remove my duplicate but the artist editor told me a mistake error message that another Core22 artist with same comment already existed. But comment was empty and there was no other Core22 artist anywhere.

I had to add a comment to enable my duplicate artist-URL relationship removal at the same time:

https://musicbrainz.org/edit/135864713
https://musicbrainz.org/edit/135864731
https://musicbrainz.org/edit/135864732