Hi again, @CassandraPresto ...
Unfortunately, I was unable to replicate things in my own sandbox course. I followed your steps...using the "Copy to" function on the "Quizzes" page to copy a New Quiz from my sandbox course to another course that I am also enrolled in as a "Teacher" (I am an admin for our school's Canvas environment). After I used the "Copy to" function, I navigated over to the destination course where I had copied the New Quiz to. The quiz copied successfully, and when I clicked on the "Build" button in the quiz to see if the questions were all there, things looked all good. I'm not sure what would be different on your end, but it might not be a bad idea to contact the Canvas Help Desk folks to see if they have any other ideas for you. How do I get help with Canvas as an instructor? - Instructure Community (canvaslms.com)
Keep us posted after you have a conversation with the Help Desk...so we know how they were able to help get this resolved for you...thanks!