Hi Mick,
Given Gary's experience with the same combo as you and your comment that you didn't experience it with the 962 after you installed "some RF chokes on the lights and oven", it would be my guess that you have one coax cable in your chain that has a poor ground connection.
I experienced a similar problem until I found the offending coax, every connection in the transmission chain is a potential offender. Interestingly enough it physically appeared OK, but obviously was not making a good connection. So you might try swapping out some coax's for better coax's and see.
?Since the Chinese so239/pl259's are so sloppy, I have removed any that I once had from my system, and in fact and switching as much of the connectors over to "N" connectors as I can, this over course means even getting Into some equipment like the tuners and switching the SO239 for a an "N", they are just a better connector.
--
Jeff - NZ2S
JeffBanke