Good morning, @ElizabethBeks ...
Unfortunately, I am not able to replicate this. In my own sandbox course, I masqueraded as a student to take a quiz that had an essay question. After I submitted the quiz, I looked at the quiz from my admin/instructor role via the SpeedGrader. I was able to copy/paste the text response from the essay question into a Word document just fine with no issues.
You might want to reach out to Canvas Support to see if they have any suggestions for you. Also, make sure your browser is up-to-date and that you have tried clearing your cache/history from your browser...for starters.
Please let us know the outcome of your conversation with Canvas Support should you choose to go that route. Thanks!