Picture stutters when buffer is on

I have been having trouble with this box over the last number of weeks; it worked fine until a few weeks ago.

The picture and sound began to stutter and I thought it was the aerial and so have recently upgraded the aerial. The picture still broke up / stuttered to my annoyance so put it down to the box.

I looked online and found that it could be the buffer being on; I turned it off and the stutter stopped and the picture clear as a bell.

But if I want to record anything and start recording on one channel, the stutter starts up again on the live TV and also on the recording.

Any ideas of getting perfect recordings and live TV