@Stephen-Rowland Hi Stephen. Yes, that's another little complication. The route I chose to get to the via point takes you on a public access road through the grounds of a stately home. During the day all those gates are open and you can get into the site one way and out the other, as you can see on the route. It's possible, as you say, that planning the route was not a problem but the navigation software baulks at it. When the software did go direct to point 5 I was already at a location where it went in via the "exit" on the planned route, right near the via point.
What I'll do is make a copy of this route and move the via point onto the road as Marinus suggested, but also make a further route that has a similar crossing of the paths but avoids going through the grounds of the stately home.
I'll update this thread early next week.
I was hoping to use MRA with Android Auto for a 750-mile ride this weekend, but its oddities with a 15-mile test route (along with locking solid and needing the phone rebooting) means I'm back to the Nav6, which is a big shame.