Hello Michelle,
Thank you for all your investigation and these updates on what you found.
The students changing the sharing permissions would definitely cause interference and relates back to the first error message you shared regarding file permissions.
Doctopus was trying to get permission from the file to check for edits and was unable to access it because the permission level had changed.
Thank you once again for digging into this error, confirming it was a permission level issue and sharing this information with the group. It is really helpful for others who may come across the same issue.