@hai991dk,
The issue comes from the Wp-Pro-Quiz plugin. Please follow the steps below toto get it resolved:
1. Open the following file:
wp-pro-quiz/lib/view/WpProQuiz_View_FrontQuiz.php
2. Find the following lines, and replace with the following ones:
2.1. line 623
apply_filters('comment_text', $this->quiz->getText())
2.2 replace with the following one:
$this->quiz->getText()
2.1. line 761
apply_filters('comment_text', $resultText)
2.2 replace with the following one:
$resultText
2.1. line 871
apply_filters('comment_text', $question->getQuestion())
2.2. replace with the following one:
$question->getQuestion()
2.1. line 985
apply_filters('comment_text',$clozeData['replace'])
replace with the following one:
$clozeData['replace']
2.1. line 995
apply_filters('comment_text',$assessmentData['replace'])
2.2 replace with the following one:
$assessmentData['replace']
2.1. line 1032
apply_filters('comment_text',$question->getCorrectMsg())
2.2 replace with the following one:
$question->getCorrectMsg()
2.1. line 1060
apply_filters('comment_text',$question->getCorrectMsg())
replace with the following one:
$question->getCorrectMsg()
2.1. line 1062
apply_filters('comment_text',$question->getIncorrectMsg())
2.2.replace with the following one:
$question->getIncorrectMsg()
2.1. line 1081
apply_filters('comment_text', $question->getTipMsg())
2.2. replace with the following one:
$question->getTipMsg()
Please don't forget to delete all caches and press CTRL+F5(twice) on the frontend before checking.