Lessons Linking To Website Home Page – Permlink?

Hi having issues with a course that has been live for a little while now. Maybe to an update somewhere along the line. However for some lessons within the course it is just showing my home page in the lesson area and similarly the home page URL in the browser. For other lessons in the same course it shows it fine and the correct URL?

Have seen previous posts about changing permalinks in settings to postname but no longer see this is an option. Also wouldnt explain why only some lessons work and others dont?? PLs help

Thanks