This was seen in revisions prior to https://en.wikipedia.org/w/index.php?title=Wikipedia:VisualEditor/Feedback&diff=561926823&oldid=561926781 and fixed in that revision.

For a reduced testcase see https://test.wikipedia.org/wiki/Section_edit_links_bug2. The cause seems to be the unclosed {{. Of course, this is broken wikitext, but the parser seems to be able to handle it fine (other than leaving out section edit links).

Sorry I can't be more specific.

Version: 1.22.0
Severity: normal
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=73182