i have a nuvi 3750 and i have uploaded europe 2016.30 ntu unlocked map and adria 4.30. All of the maps are showing under my maps but only adria is showing map routes on display. when i choose any city from europe 2013 screen is blank . no streets no nothing. what could be the problem

The version of 5.10 of the firmware from 24/10/2016 it is supposed that
"Changes made from version 5.00 to 5.10:

Added improvements for handling larger map files."
So most probably there is a problem on this changes i could propose to reverse back in 5.0 firmware!