I have finally sussed out an issue I have had for a while. It ssems quite regular, maybe even happening every time.
The issue is the unit playing back, but becoming unresponsive, as mentioned by Jimmy22 above. This seems to occur when a recording finishes during a playback.
Situation tonight, was watching the News, and rewound to see Ted Cruz elbow his wife in the face. No issues (for the unit a least). 5 minutes later, Shortland St finished recording, and Fair Go started recording. Saw the "Successful Recording" message in the bottom corner. About a minute later, went to pause the News, and you see the info banner at the bottom show the pause, but the time scale is at 0:00 and not advancing. It is playing back, but not playing back.
This seems to happen regularly as we tend to hardly ever watch live TV, recording any shows we are interested in.