I do the same, import the file by "send to device" then either choose the SD card or the Device.
Weirdly, the route shows differently in BC to start with though. If i click the route form my Home Address to the ferry port in the more basic map it gives me "basic route" with a lot less detail on it. If I click the map that is stored in my SD card, It takes me the route I actually want to go. I think the final key here is working out why it seems to want to continue to use the older less detailed map as opposed to the newer one?
So in "my maps" do you have all the maps ticked?
CN Europe NTU 2017.10 ALL
Europe DEM
CN EUROPE NTU 2017.10 3D
My 590 only has Europe DEM & CN Europe NTU 2017.10 all both ticked

