On Unit Page(s) I'm unable to add and save new elements.

I've recently developed a training site for our business using Corusepress Pro, and up until now has worked great. Until I created a page where the students could upload their work. Now when I save the page the elements either are not saved (displayed) or added.

The strange thing is that if I 'dup' the course and go to the cloned page I see all the attempts to add the element.

I am lost here.