The satnav in my new to me 2015 RRS Autobiography Dynamic has been working fine, but today the map was showing only a few roads & loads of white contour lines, whether I selected On Road Navigation or Off Road Navigation; the only difference to the displayed map was in Off Road Navigation I could tap on a "Trail Line" (or similar?) button. It is as if it is serving up the same map in both modes.

Has anyone else experienced this, and/or how to resolve the problem.

TIA