We have had some issues also. My Media guy and I went around the horn over the types of files I could use. He thinks you are going to have to mess with the encoder settings. Lectora uses the old extension mp4 while Apple uses m4v. We solved this by just literally changing the extension. Crazy, right! Obviously, we are using Apple software. I am not sure about Adobe. Hopefully, someone else will have more info for you.
Are either of you able to share the course files where this issue persists? The development team would like to take a look. You can submit a support ticket at firstname.lastname@example.org or I can forward the files if you email me at Jennifer.email@example.com. If the file is to large I suggest reducing it down to only the page in question or using WeTranfer to send the files.