If it is as I said (i.e. resistance increasing from 0.139 M Ω to 1M Ω, then that's probably not far from what one would expect - but, as eric said, that doesn't mean that a fault would not show itself if it were tested at a much higher voltage than a multimeter uses. I therefore fear that you have not moved too far forward.Hi John ... I think it is as you have said
Kind Regards, John