One-timer: run recountCategories.php on the wiki server
This is kinda one-timer - we need to run the maintenance script recountCategories.php on the wiki to fix the counts of category members in the database. See this discussion for details.
php maintenance/recountCategories.php --mode=pages
php maintenance/recountCategories.php --mode=subcats
php maintenance/recountCategories.php --mode=files
Not a high priority, but would be nice anyway... CC @grazzolini @jelle