At https://bugzilla.wikimedia.org/show_bug.cgi?id=65779, the URL field is set to https://en.wikipedia.org/w/index.php?title=User:PleaseStand/Sandbox&oldid=610241510.
However, at https://bugzillapreview.wmflabs.org/T3084, the URL added to the description is https://en.wikipedia.org/w/index.php?title=user:pleasestand/sandbox&oldid=610241510.
In this case, the link was not broken, though in other cases it could be. Lowercasing capital letters in a URL, except in the scheme and hostname, often does not preserve semantics, so the migration script should not do that.