We've had a couple of instructors notice a new issue when grading in Dropbox. Certain pdfs turned in to Dropbox behave strangely when we try to highlight a section and copy it into something else.
Here's an example in a video:
A live course that is having that issue is this one:
Jaclyn Roberts paper for the Chapter 5 Dropbox behaves this way.
I wonder if this is related to the recent PSPDFKit Annotations tool update in Assignments.
https://learning.greenville.edu/d2l/home/261094