I take it the problem was not evident while the various tests were made.
I have also found it necessary, (sometimes at inconvenience to one's self) to attend on site at abnormal hours to actually catch the fault happening, as it may not be possible to ascertain from measurements alone the mechanism behind the fault.
Without knowing your existing distribution setup, ie what type of channel filtering/channel distribution map etc is in use, maybe your ABC problem can be overcome when Table Cape comes on line.
Appreciate the comments, he mentioned that they can move up and down frequency but also can lock on to one and stay there .. and your guess was correct the problem wasn't apparent when he was doing the tests ( maybe the offending property wasn't watching TV !!) The problem was there when the guys from RAS where checking our MATV system two days before but seems to be intermittant at the moent
I'm just going to have to put up with it until Table Cape comes online..