Quantum DVR (Arris) will suddenly now show storage at 100%, when showed in the 80's a day or hours earlier. Rebooted and capacity went back down to 83%. Back up again to 100% one day later with only one or two new programms recorded. Otherwsie seems to operate fine. (VHO4)
Have you tried rebooting the box?
If so, I would contact support.
Sounds like box may be failing.