Elements not saving inside units

I have a course with 26 units. I added the first unit ok but have added another 4 and the elements inside them have not saved. Have been back and tried a dozen times or more now and elements are not saving. I notice this is a long standing bug that the developer has claimed was fixed but that is obviously not the case. Any idea when this will be fixed?

I have opened the site to you if you want to take a look