Montana 700i Crashes - City Navigator Stop Navigation

I have a Montana 700i that I mostly use for trail riding etc using Tracks created in Basecamp which all seems to work OK.

However if I select the City Navigator map and then navigate to a waypoint it calculates and navigates the route just fine. But when I select Stop Navigation the unit crashes.

A reboot (long power button press) doesn't solve this as trying to stop Navigation again just crashes the unit.

The only way I have found to stop this behaviour is to calculate the route with the CN map, then switch it to Topo Active. The route still works, and it's then possible to Stop Navigation without a crash.

I also have the 1:25k Topo GB Pro maps loaded to the device (but not activated).

Plenty of space on the device an SD card.

Anyone else had this issue, or know of a work around as its very annoying having to switch maps just to stop navigation without crashing the unit