I have a course with units that have questions that require an answer. So in the units list, all units except the first one are locked. Which is normal from what I understand. BUT if I just go to the course details and click on the units from the course structure list, I can access the units (or if I enter the URL manually too). And free preview is not even on, so definitely there should be no way to access them.
Quick preview: https://youtu.be/m1UmodFkSOw
I have granted support access.
(I also have another topic started with an issue about unit access, but I think it is a separate issue, still here it is.)