How can I fix my Humax 9200?

My Humax 9200 has started being fussy about what it will record. Some pre-scheduled programmes do not record, sometimes immediately following others which record successfully. The record icon appears on-screen during the programme but it's a lie. If i realise the programme is not recording, I can't cancel the pre-set and record it manually: in fact the one touch recording seems to have stopped working.