This may be a different issue than Alan's, but he hasn't yet supplied a file. When you refer to "saving" the file, are you exporting it?
Let's see your mp4, and we'll get to the bottom of this. Sharing is easy and takes but a few minutes. Just follow this instruction...
Upload the file/s to a free server, such as Google Drive or MS OneDrive, get a shared (public) link, copy the link and paste it here or to me in a Private Message via the mail envelope in the top-right corner of this forum. When using Google Drive, if necessary change "restricted" to "anyone with link can view."