Sony BVM 2011P potential sync issue

This is what happens to my Sony BVM 2011P when I connect any of my consoles to the RGB input using EXT Sync. I am using a Female RGBS SCART to BNC adapter from www.retrogamingcables.co.uk. I have the R, G and B connected to the R, G, B inputs and the yellow sync cable is connected to the EXT SYNC connector. The monitor is set to RGB mode and I have restored factory defaults. The cable works fine on my Sony PVM.