Downloading Videos

I'm trying to download a video from my doorbell camera.  When I view the video on my app, I can see the full 1 minute and 5 seconds.  But when I try to download or share the video, it only saves 3 seconds.  Viewing the video on my computer is the same - just 3 seconds.  Has anyone else experienced this and how did you fix it?  The video is important as it shows the culprit of property damage...