PHP notices are being thrown, because they haven't been linked to the main alias file in extension.json. They should be.
Hmm, looks like its thrown by conflict with extension/mediawiki setting? Also has this problem, cleared LocalSettings.php, and problem disappeared. Need to recreate this again, and find exact extension/mediawiki setting. Appeared in QuizGame.
There are some extensions, which using just "$aliases" in the alias file, not "$specialPageAliases"
ArticleRatings Challenge FanBoxes SpecialNamespaces SportsTeams UnusedRedirects UserExport Video