Reported by <rotpunkt> on #wikimedia-dev.
<rotpunkt> Hi, there is a bug with tag ref, see table of content in http://en.wikipedia.org/wiki/Ambernac.
<andre> An ?action=purge on https://en.wikipedia.org/wiki/Allenwiller shows the same error now.
<rotpunkt> andre after refreshing the cache (action=purge) the problem is also there
<anomie> At a quick check, it looks like https://gerrit.wikimedia.org/r/#/c/181112/ slightly changed the behavior of <ref> in headings, and https://gerrit.wikimedia.org/r/#/c/213313/ really changed it in response to T99787