Anonymously reported on IRC.

When editing an artist having two relationships to two distinct URLs having the same normalized form (and the same auto-selected relationship) results in an error “This relationship already exists.” that blocks editing the artist (unless you remove both URL relationships, which is not wanted either).

Example:

Klaas Heufer-Umlauf (MB artist) had two URL relationships of type “other databases”:
1. https://d-nb.info/gnd/1027779468 (MB url) added in 2019 via edit #63989307
2. http://d-nb.info/gnd/1027779468 (MB url) added in 2020 via edit #74416052

Their normalized form is 2. http since MBS-10534 (2021-04-19).
URLs have been merged since in edit #82026387.