Board Thread:Support Requests - Getting Technical/@comment-4189499-20150607233806/@comment-24473195-20150927071621

It is because of cache. The page was originally saved as part of a particular category, and that's when the cache was set. Later on the category was changed but the page didn't change because as far as the wiki is concerned the source code and the page are still the same.

Unfortunately, it was  designed to save bandwidth and processing time. You could try to contact staff to see if its a bug on their side. The only other solution I can think of is for a bot to automatically update those pages thereby forcing mediawiki to refresh the cache.