Module created under content suddenly not appear or "hang"
I have spent hours to create module and it's sub-topic together with the learning activities for each sub-topic. I always click the button "done" and "save and exit" after finished upload or key in data in widget or quiz. Unfortunately, when I want to re-visit the page and see the course content editor, suddenly the module created disappeared or the page became "hang" (only for course content, other button is okay). Cannot do anything about it. But completion status showed 63% completed. Is there any possibility that all data upload and created missing? and How to get back the data?
Your explanation is greatly appreciated.