We recently found an issue when taking a quiz with the Lockdown Browser. An Instructor brought to our attention that a particular quiz was freezing when a student would attempt to save their answer. We later found out that the issue was more specific to how the video was being used in the quiz.
Some considerations should be taken when using video. There are many places to embed video from many different sources. We would like to see users embed iframe videos i.e. (YouTube) in the question text. What we saw some people doing was they were adding the YouTube videos in the Header/Footer area of the quiz. This was causing the quiz to freeze for students.
What you will need to do is modify the copy code from YouTube and change the initial HTML tag from iFrame to object.
With this solution you will now be able to have videos in your quizzes without Lockdown Browser preventing students from saving.