[DrGeorgeReid]

Thanks for the suggestions. I've tried re-setting the road-sign information option in the central display. Option was selected (green) but still no road sign display.

Today, I noticed that if I started driving before the nav system had booted up the road signs were not displayed but if i waited until the nav system was ready the road sign symbols were displayed. I was updating some of the maps via a USB stick when the problems occurred. Perhaps the updating process slows down the nav system boot up.