Just wanted to add that the page failed to show in both of the categories it was assigned, so the issue doesn't appear to be anything specific to Category:ChangeReadyForWrangler. Since Ben edited the page, it's now listed in both Category:ChangeReadyForWrangler and Category:SelfContainedChange — the two categories that were always showing (as working links) on the bottom of the page, ever since it was created.

This sounds to me like a caching issue. Next time it happens, can you try purging the cache of the category page (and perhaps the page being added?).

https://www.mediawiki.org/wiki/Manual:Purge explains how, but mainly just go to the page and throw ?action=purge at the end of the URL, then press the button that shows up.

I'm going to close this now, but do reopen or file a new one when/if it happens again and we can make sure it's just a cache issue.

Reopening since it happened again. I did a purge of the category page as suggested, to no effect.

It seems to be a MediaWiki a parser error, of some sort, rather than a cache issue.

If I go to Special:ExpandTemplates and fill in the following wikitext:

{{:Changes/RemoveGlibcHeaders}}

(which does nothing but transclude the entire article contents), the [[Category:ChangeReadyForWrangler]] link does not appear in the processed output. It's getting dropped for some reason.

If I copy-paste the entire wikitext source of Changes/RemoveGlibcHeaders into the wikitext field, same result: The ChangeReadyForWrangler category is nowhere to be found.

Hah! Oh, wait, I see it.

The text preceding that category (line-wrapped for clarity):

<!--- UNCOMMENT only if this Change aims specific product, working group
 (Cloud, Workstation, Server, 

== Current status ==

[[Category:ChangeReadyForWrangler]]

So, false alarm. It's a source issue.

@ferdnyc Indeed, thanks for spotting it. I've fixed it.

D'oh! Thanks for catching that @ferdnyc! I'll re-close the ticket until/if it pops up again.