I bought a Thompson DT1000 Freeview stb and it worked fine on my Mum's old Panasonic 4:3 TV in RGB mode. But I recently set it up on my sister's TV (again an old Panasonic TV, but newer than Mum's). When I set the STB to RGB and switch to any analog channels there is a 'rolling' picture of the freeview channel coming through. Switch the stb to composite and it's fine. The scart leads are fully connected 'out of the box' cheapo type but worked OK before. Any ideas?