This is one issue which appears when buddypress settings are not properly done, or you disable few components. Since the Demo data courses are connected with the groups and forums, when you disable BuddyPress groups, forums and you do not edit the prebuilt courses, all you see is the truncated data.
Simply edit the course you’re viewing and re-save/update it again.
That will automatically correct the settings and resolve this issue.
When you create a new course there are no connecting groups or forums and hence the newly created courses appear fine.