When a minor change (such as moving from http to https) is made to an external link from the artist editing page, it creates another URL entity and changes the Artist-URL relationship to point to the newly created URL. See edit #74100275 for example.
The external link fields of entity editing page should probably create an "Edit URL" edit (see edit #73843177 for example) rather than "Edit Relationship" edit with a new URL entity under any of the following conditions:
- The new URL is the clean form of the the old URL according to URL cleanup.
- The new URL differs by its scheme only (for example http to https).
- The new URL is missing a specific subset only (query ?... and/or fragment #...).