My problem with the re-occuring VU freeze after a few minutes to an hour or so is now sorted.
I got a bit frustrated and even changed the power supply but it still acted the same way.
The cure:-
After a period of time, in these cases many years, the ribbon cable can oxodise on the connector spikes, especially when there have been many reseats.
This time when I did a reseat, I run my thumbnail between the ribbon and the connector to gently lift the wire off the spikes, I then clamped it down hard with a pliers, it has now run for eight hours without any problems, before, I was luck if it run eight minutes.
Worth a try guys
Phil