If you selected "Prevent Skipping" but it seems like your students are still able to skip parts of the video, don't worry!
The student is probably using a smartphone or a tablet to watch the lesson. It's harder to track the students when they use these devices, which is why we have apps for iOS and Android. Make sure your students are using one of the following:
If they're using these correct devices and versions, progress should be tracked much more effectively. If you continue to have this problem, please let us know at email@example.com and we'll take a look!