Right, here goes:
(1) I have received a sample route from the OP, it's for the Romantic Road, Wurzburg to Fussen
(2) It's a GPX exchange file, so it opens straight up in BaseCamp, which shows it as being created in Motorcycle mode. I have attached a copy, hosted on Dropbox for others to try.
https://www.dropbox.com/s/1aqf8yu8fy1l47y/Romantic Road.GPX?dl=0
(3) My Mac is running exactly the same maps as the OP
(4) The first thing I have noticed is that the route is shaped by announced waypoints (as opposed to unannounced shaping points) but that alone should not create a problem when displaying and then running it on a Nav V
(5) I also noticed that all the announced waypoints have the same arrival time and that the start point at Wurzburg has the same time as the arrival at Fussen. In short, 237 miles taking no time at all.
(6) I have imported it into a Nav V, which is running exactly the same maps as the OP.
(7) The route imports well and comes up on the screen just fine. A magenta line between Wurzburg and Fussen of 238 miles (I wouldn't worry about the mile difference, it's probably a rounding thing) but also now shows a total journey time of 6 hours 20 minutes.
(8) As one would expect, each of the OP's waypoints are shown as little orange flags. The device has also calculated a total journey time (something that wasn't shown on the computer version in BaseCamp) and has also given an arrival time at each of the waypoints.
(9) I can review the trip on my Nav V and all the turn by turn instructions are there in a route card format. The only thing that's changed is that the estimated journey time has then reduced to 5 hours 40. That is nothing to worry about, it is simply the device 'knowing' that I'll ride it faster that the software thinks i should. In short, it 'knows' I'll speed.
(10) From my home in central London, I can ask the device to navigate me to the start of the route and / or to the end point and / or to all or any of the waypoints in-between.
(11) I have repeated the same process using two other Nav V's with the same overall satisfactory results.
In short, it all works and I'd be happy to use it.
Now....
The OP's route seems to be well created in BaseCamp and works OK in no less than three Nav V's. It's a moot point whether the OP should use unannounced shaping points as opposed to waypoints when dragging and fixing a route but let's not debate that here as it should make no difference.
The OP tells us that the route looks OK on his Mac, just as it does on mine. Let's accept that.
The OP tells us that the route only goes haywire when he displays it on his Nav V, whilst it doesn't on three of mine. Let's accept that, too.
The problem therefore can only lie in the OP's Nav V device - maybe in the maps - OR in a difference in the settings between his Mac and his Nav V device OR both. To try to walk us through that problem I have attached a link to a version of the same route that I have created, to see how he gets on...
https://www.dropbox.com/s/4i7exsa2fyajqup/Helping the bod out..GPX?dl=0
I have coloured the route red.
It is showing as being 236 miles, an insignificant difference in distance, probably just because I sometimes didn't go exactly to each of the OP's waypoints, which are based in towns.
The time taken is 6 hours 1 minute. Again, an insignificant difference, probably just down to differences in the personal set up of BaseCamp on my Mac versus his.
I made sure that the BaseCamp software on my Mac was set to fastest time, in Motorcycle mode and that all the routing 'helpers' were turned off. In short I would be in charge, not the computer. I then simply asked BaseCamp to take me from A to B (Wurzburg to Fusson) and then shaped the route using the shaping point arrow in BaseCamp to drag it over the OP's route. This created announced waypoints, which i then converted into unannounced shaping points.
My version of the route runs fine in each of my three Nav V's. Does it work for the OP.....????
Richard