OP
beachlover
Well ok then I'm going back to my original idea;Power quality analysis. If your PV is doing strange things then it would be picked up. I can't really see where or how you can investigate further without such an approach. I think I agree with DavisonP, turn off your PV inverter and see what happens.
Does PV mean asking the electrician to turn of the solar panels?
I'm making a list of everything everybody has said so when the electrician turns up Monday I can put forward your suggestions .