In my OP at the top of this page I gave a link in "this example". I just tried that link again and it is still showing a very unhelpful diff.

PageImages probably needs MediaWiki:Pageimages-denylist to exclude some images that are fine for their purpose but not useful for PageImages. However, PageImages should also exclude items at MediaWiki:Bad_image_list. A picture of anal sex is fine at an article about that topic but there is no encyclopedic value in showing it when searching.

This problem also occurs in the Wikipedia App (tested with the WMF iOS app). That is, typing "ana" to search in the app shows the image. A robust low-level solution is needed so MediaWiki:Bad_image_list images are never displayed except at the appropriate article.

@Aklapper Please clarify because I'm not sure if you think this request is a user problem or a database error that needs to be fixed. It is not possible to create
https://bn.wikipedia.org/wiki/Template:Arguments
On visiting the page, "Error" appears where the title should be. On trying to save an edit, an edit conflict error is shown.

Convert is unbelievably complex. When embarking on the process of translating the 4000+ templates used prior to the module (June 2013), I had the programmer's glow of confidence but that wilted on discovering how many quirks convert has. Something might be 12 feet (3.7 m) long, or 12 ft (3.7 m) or 12 feet (3.7 metres) or 12 feet (3.7 meters). Or perhaps you have a 12-foot-long (3.7-metre) something. Then there are a bunch of rounding options and ranges, for example 2 by 3 by 4 inches (50 mm × 75 mm × 100 mm).

@Vachovec1 The module I wrote was originally Module:Country because I thought it would be enhanced to cover more than Europe. The module was moved and I explained my plans at c:Module talk:Countries of Europe. In a few days I am likely to have something to demonstrate and we could decide on a better name such as Module:Countries.

@Jarekt c:Category:SVG logos of the United Kingdom no longer has a problem, but that is because I implemented the template with a module which uses mw.wikibase.label. See T171392#3587254 above for a table comparing the performance of the old template with the module—the module uses under 0.05 seconds and 1.2 MB. Some notes on the reduction in the number of pages listed at the error category are at template talk.

My understanding of the situation is:

• HHVM rather than Lua catches the error when the Lua memory limit is hit.
• That can result in "503, Service Unavailable" responses.
• c:Category:Pages with script errors lists many pages that are using c:Template:Countries of Europe and which hit the memory limit.
• The problem may be reduced or avoided by reworking c:Module:Fallback.

I updated Module:Country and believe it now displays the same result as Template:Countries of Europe. See the demonstration at module talk and the discussion at template talk. As far as I know there is no realistic way of comparing outputs from the current template and the sandbox template (which invokes the module) for all possible languages, so replacing the current template would be courageous, but it would avoid the out-of-memory errors.

Following a discussion at en:WP:VPT I wrote a very small module (commons:Module:Country) to test the overhead from fetching the Wikidata label for each country in Europe. I used a generic module name in the hope that I might extend it to provide a more efficient alternative to commons:Template:Countries of Europe.

Using Special:Search for "data.schemaVersion must be a number" (with quotes) shows many of the mw.wikibase.entity.lua at line 37: data.schemaversion must be a number, got nil instead problems. That applies at enwiki (330 pages listed), but itwiki wins with over 5700 pages. Possibly the problem pages are noticed and purged more quickly at enwiki.

The new error message was mentioned at en:WP:VPT and I replied that it is part of the "what exactly the problem is" patch mentioned by hoo above. I also noted that I recently purged articles with script errors, and it is currently adding about four articles per hour.

Any comments about my guess in the initial report? I speculated that php.getEntityId in mw.wikibase.lua sometimes returns junk due to a timeout when it tries to establish a network connection with the Wikidata database (that I know nothing about).