This is the third time in two months that a part of a quiz that existed when I tried it in "Preview Mode" suddenly disappeared once students tried to take it.  It has been three different quizzes in two different classes. On the most recent one, the first two students who took the quiz had no issues, but then the next few who followed were only able to hear the audio file, while the part where they were supposed to fill in the blanks was completely missing.  When I went back to check in preview mode, sure enough- it was gone.  I put it back in and the remainder of the students had no issues. 

This is truly odd and I can't figure out why this is happening. 

These quizzes all use lockdown browser and webcam.