We recently had this brought to our attention and then one (Jackie C) of the people in my support office did wonderful followup research on it, but now we want to know if others are have seen or are encountering this issue. [Note, we've opened a support ticket with Canvas as well.]
But here's what we have:
If a teacher gives extra time on a quiz while student are taking the quiz, the extra time will not override the lock date but will override the timer the students see which causes the appearances of issues to students taking the quiz. The students also receive a message that they have been given extra time. Jackie did a screencast: http://www.screencast.com/t/YTqnbrf0
But she also provided a summary of the screencast:
In this screencast, I have two screens up. The instructor account is on the left, and the student account is on the right. I start by moving the lock date up to a time in the near future to make sure that a student that starts the quiz would not get the full 10 minutes for the quiz. As a student, I start the quiz. It warns me that I only have ~2 minutes of the 10 minute quiz. As a teacher, I change the time limit to 12 minutes. Immediately, the student gets a banner that says "You have been given extra time on this attempt." The quiz timer updates to reflect the 12 minutes the student has, but the lock date remains the same. One minute before the lock date, the student receives a banner that warns about a late submission. However, once the lock date passes, Canvas does not kick the student out. The student has to refresh the page to get kicked out. Once the student refreshes the page, it shows the quiz was locked at the lock date, but it doesn't show the current submission. As a teacher, I can see that the student's quiz attempt is still counting down in the moderate quiz tool. (I change the timer to 1 minute at this point to cut down on time.) After the timer counts down completely, the student can finally see the quiz submission. In the moderate quiz tool, the student's countdown changes to Time Up!
Important things to note:
-Any answer marked after the lock date (regardless of whether or not the student clicks Submit Quiz) will be saved.
-In a one-question-at-a-time quiz, moving to the next question after the lock date kicks the student out.
-This behavior occurs in multiple browsers (FF 45.0.2 and Chrome 49/50)
-The extra time can be granted through the actual quiz settings or through Moderate This Quiz; the behavior is the same.
So, intended behavior or not?