Seen on https://logstash.wikimedia.org/app/kibana#/dashboard/mediawiki-errors for "Quiz", since at least the 1.32.0-wmf.7 branch. About 50 records currently in Logstash (July 2018).
exception.message PHP Notice: Undefined index: 3 exception.file /srv/mediawiki/php-1.32.0-wmf.14/extensions/Quiz/Question.php:380 exception.trace #0 /srv/mediawiki/php-1.32.0-wmf.14/extensions/Quiz/Question.php(380): MWExceptionHandler::handleError(integer, string, string, integer, array, array) #1 /srv/mediawiki/php-1.32.0-wmf.14/extensions/Quiz/Question.php(186): Question->basicTypeParseObject(string, string) #2 /srv/mediawiki/php-1.32.0-wmf.14/extensions/Quiz/Quiz.class.php(324): Question->multipleChoiceParseObject(string) #3 /srv/mediawiki/php-1.32.0-wmf.14/extensions/Quiz/Quiz.class.php(246): Quiz->parseQuestion(array, boolean) #4 /srv/mediawiki/php-1.32.0-wmf.14/extensions/Quiz/Quiz.class.php(151): Quiz->parseQuestions(string) #5 /srv/mediawiki/php-1.32.0-wmf.14/extensions/Quiz/Quiz.hooks.php(28): Quiz->parseQuiz(string) #6 /srv/mediawiki/php-1.32.0-wmf.14/includes/parser/Parser.php(3898): QuizHooks::renderQuiz(string, array, Parser, PPFrame_Hash) #7 /srv/mediawiki/php-1.32.0-wmf.14/includes/parser/Preprocessor_Hash.php(1188): Parser->extensionSubstitution(array, PPFrame_Hash) #8 /srv/mediawiki/php-1.32.0-wmf.14/includes/parser/Parser.php(2953): PPFrame_Hash->expand(PPNode_Hash_Tree, integer) #9 /srv/mediawiki/php-1.32.0-wmf.14/includes/parser/Parser.php(1297): Parser->replaceVariables(string) #10 /srv/mediawiki/php-1.32.0-wmf.14/includes/parser/Parser.php(446): Parser->internalParse(string) #11 /srv/mediawiki/php-1.32.0-wmf.14/includes/content/WikitextContent.php(323): Parser->parse(string, Title, ParserOptions, boolean, boolean, integer) #12 /srv/mediawiki/php-1.32.0-wmf.14/includes/content/AbstractContent.php(516): WikitextContent->fillParserOutput(Title, integer, ParserOptions, boolean, ParserOutput) #13 /srv/mediawiki/php-1.32.0-wmf.14/includes/poolcounter/PoolWorkArticleView.php(145): AbstractContent->getParserOutput(Title, integer, ParserOptions) #14 /srv/mediawiki/php-1.32.0-wmf.14/includes/poolcounter/PoolCounterWork.php(123): PoolWorkArticleView->doWork() #15 /srv/mediawiki/php-1.32.0-wmf.14/includes/page/Article.php(604): PoolCounterWork->execute() #16 /srv/mediawiki/php-1.32.0-wmf.14/includes/actions/ViewAction.php(68): Article->view() #17 /srv/mediawiki/php-1.32.0-wmf.14/includes/MediaWiki.php(500): ViewAction->show() #18 /srv/mediawiki/php-1.32.0-wmf.14/includes/MediaWiki.php(294): MediaWiki->performAction(Article, Title) #19 /srv/mediawiki/php-1.32.0-wmf.14/includes/MediaWiki.php(867): MediaWiki->performRequest() #20 /srv/mediawiki/php-1.32.0-wmf.14/includes/MediaWiki.php(524): MediaWiki->main() #21 /srv/mediawiki/php-1.32.0-wmf.14/index.php(42): MediaWiki->run() #22 /srv/mediawiki/w/index.php(3): include(string) #23 {main}