I have had the same problem with my magictv in christchurch. It didn’t recorded any of my programmes on Sunday night. I think I have fixed it now I switched it off at the wall for 30 seconds and once it restarted I went into the setup menu and did a new auto channel scan to replace all the current channels.
I have had other issues with the box earlier last week when the sound kept cutting out on live tv3 and c4 but was fine watching a recording of the same broadcast. That seems to be fixed now also.
Hey I have helped someone in Chch with the same problem and it turned out to be the signal from the Sugar Loaf was too strong for the MagicTV. This place was line of sight to the Sugar Loaf. So the solution was to get a dB Attenuator from Dick Smith. This reduced the signal a little and it all worked fine. I think it was the 6db Attenuator.
As silly as it sounds, you can usually do the same thing by using rabbit ears instead of your outside TV aerial.
If the problem occurs again I would suggest checking out this as a solution.