DigiFusion freezes?

FVRT150 DigiFusion Video Recorder - picture freezes on playback of some recorded programmes, usually at the same point. The only way to recover is unplug power and then power up while holding in the 2 rightmost buttons for as long as 'hold' is displayed. I have cleaned all dust and fluff out of the machine and checked operation of cooling fan for disk drive.

Does anyone have a cure for this freezing problem?