One of the key reasons I upgraded to the 530 from the 520+ was the speed of calculation and native MTB Navigation capability. I've honestly been disappointed on both counts - and I suspect the two issues are related.
I create a Ride Plan in Trailforks and then use the Trailforks ConnectIQ app to navigate - the native MTB Trail navigation apparently does not work unless a public route exists for the trail network. Coming up to a trail intersection (and in a dense trail network there may be a couple within 100 feet) the "Turn Warning" often is triggered after passing both intersections leaving you unsure of which one to use (I did not memorize the route before I left home) after the dreaded "U-Turn" signal is triggered. It's really frustrating.
Has anyone figured out a workaround? Is the native navigation any better?