Hi KarenMatson,
Given that it sounds like it is happening to a fair number of users, it may be that you need to reach out to Canvas support for further assistance, as it could be something that is able to be replicated on that video on their side, or it could be something occurring with your PC's and network. If your student's haven't yet tried another browser, or tried clearing their browser's cache and cookies, those would be good steps to do first.
I'd recommend also recording a video or screen-recording of the issue and what the students see, and including a link to that when you reach out to Canvas support.