Not sure if your issue has been resolved, but if not, try this. I know the interface is different depending on your version, but it should be similar. On mine I go to HDD manager, look at the tabs on the top. Click on Storage Setting. Set "overwrite" to "auto". I had a firmware upgrade in the past and after the update this got changed to "Manuel". I changed back to auto and all was well. I suppose if for some reason you had activity recorded that you were afraid to lose, you could stop the overwrite until you were able to remove the video.