The conditions for when to insert <span class="name-variation"> and when to insert the corresponding </span> are out of sync. This may cause a </span> closing tag to be created, which then prematurely terminates a different <span>.
E.g. on http://bitmap.mbsandbox.org/artist/7e84f845-ac16-41fe-9ff8-df12eb32af55/relationships, the second relationship should be all yellow (including the "(background vocals)" part) because of pending edits, but isn't. This is the HTML: