If you change the point value of a quiz in Quizzes.Next after students have taken it, the number of points possible will update, but student's scores will not automatically adjust to be the same percentage of the points possible.
For example, let's say you create a quiz worth 5 points and a student takes it and scores 5/5. If you then change the point value of the quiz to be worth 10 points instead, Canvas will change the points possible in the gradebook, but will not automatically update the student's score to 10/10.
Assignment Details Page:
Versus the Gradebook:
The workarounds are to either regrade a question that doesn't need to be regraded (which will push through the updated scores) or add fudge points to each submission (which could be time-consuming in a large course). Since not all question types can be regraded, it would be great if Canvas could automatically update student scores to be out of the same percentage of the points possible.