Thanks for the reply
Yes, I have put the cables back into the ports that have not worked and they have then worked.
I connect to, say, ports 1, 2, 4, and 4, everything wil be fine. I ill then go back at soundcheck time and 1 or 2 of the lights will be solid.
I am using 3, 5 or 10m cables. I also have a 10m 4 way loo which I send round the stage which then goes 4 ways via 5m cables.