Have you watched the driveshaft when this is happening. I have an Axis 500. And had the splines on the drive shaft bad and the cup on engine bad. Replaced both and have been great for almost a year.
If not the drive shaft/cup, then I going to guess it is something inside the rear differential.
As far as the video goes. It would be better to upload to YouTube. Set it to anyone with a link and post a link to it. I had to download and play with VLC to watch.
Were you on a hard pull, level or going uphill when it 1st happen?