Lost imported audio and video
Imported audio to each slides, and added one page with imported video. preview looks normal. After put into package as a zip file, reopen the file from package, the audio and video are lost.
I made 4 courses about same number of pages, two of them behave normal, and another two behave like above: lost audio and video after put into pacakge. What I found is that the ppta files for the two abnormal ones are of very small size (please see attachement, BV-1 and BV-4 are abnormal ones which show very small size in ppta files)