Your Humax is miss-tuned. This is causing it sometimes to look at the wrong transmitter for the next programme in the series. Because it is looking in the wrong place it does not find it and therefore does not record.
A summary of what to do if you are using firmware 1.00.23 is:
1) Identify which tranmitter is the best tranmitter for your current aerial;
2) Get on the internet and identify which 5 UHF channels that transmitter broadcasts the non-HD channels on;
3) Action an auto-tune and then cancel it without saving any found channels.
You should now not be tuned into any channels and not be able to switch channels because there are none there anymore;
4) Check that you are not tuned to any TV channels. Check that you are not tuned to any Radio channels;
5) Navigate to the manual tune menu. For each of the 5 UHF numbers action a manual retune. You will not need to enter any other details when you do this;
6) Tune to one of the BBC channels and leave it a couple of hours for the epg to fill up again;
7) Setup your favourites and your schedule (timers) again.
A useful internet site for both1) and 2) is http://www.digitaluk.co.uk/postcodechecker/main/index/dummy/NA/yes. Put in your postcode and be sure to have the "I am in the aerial trade" box ticked. You will need to scroll down to the digital details for your transmitter. The UHF channels are the ones on the row that starts with 'now'. They will be in the range of 21 to 69.
If you do not have the "I am in the aerial trade" box ticked it may not give details for your best transmitter for your aerial. Also you will then have to find 'show more details' for the UHF channels.
If your firmware is earlier than 1.00.23 then instead of an auto-tune/cancel you will need to action a Default Setting with the aerial disconnected. To be on the cautious side be sure to totally power OFF the Humax when connecting/disconnecting the aerial.
NS
October 2011