I've got a bit of a quirk - I've got a course that's got a several 'items' - each with some content. In most cases, the content can be seen whether edit mode is on or off. However, there's on that has isn't visible when the edit mode is on - you have to disable the edit mode to see the content.
The section that's not showing as expected had a lot of span tags in the HTML, (I'd used the inbuilt editor to create it) - I deleted them, but no difference (then I check the one that's showing with edit on & that's also got them).
Somewhat mystified as to why things can't be seen in the one case. It's not a great problem, but it is annoying - and I could see some staff getting confused if their work isn't apparently visible ...
EDIT MODE ON:
EDIT MODE OFF: