Basecamp to Drivesmart recalculates and changes the Route when loading.

Not really since above you say you're selecting the end point, if you do that then as I've already stated a new route being calculated is how it's designed to work. If you want to follow a route select the start point or any other viapoint depending on where you want to join the route.

Try this simple test. Create a route with a start and finish point, insert two via points and a shaping point between them all, so you have a route starting at A, going through B and C, then finishing at D. You have 3 shaping points, 1 between A and B, 2 between B and C, and 3 between C and D.

Your route is therefore A to 1 to B to 2 to C to 3 to D. Send it to your device. Select the trip planner App and select Go to A. Your device should then calculate a route from where you are now to A then it should follow the planned route. If alternatively you select D you'll be sent directly there. If you select B you'll be sent to B, then 2, C, 3 and D. If you select C then you'll be sent to C then 3 then D.

If that isn't happening please post a screenshot of what you see in Trip Planner.

I can see Technoguppy has a Zumo, could you please confirm what you have?

Just to clarify;  I create shaping points in Basecamp by dragging the route.  That creates an Alert point.  Those show up on the Drivesmart as selectable points on the route (after pressing go).  If in Basecamp I change them to "do not alert"  They do not show up so if you are already into the route you can only select the start or the end and therefore you lose the shaping points (unless you go back to the start).  More clarification below.

Well that's exactly how it should work. If you want the option to select them don't change them to shaping points ;)

I have 3 Garmins and have run identical test on the 3.  I will attempt to detail the results here.

On a Nuvi when you call up the route from Basecamp you can either load the route without recalculation or you have a choice to recalculate.  If you do not recalculate it locates where you are and continues on the route from BC.  I consider this to be the optimal programming.

On my Drivesmart61LMTS and Drive52m they behave the same.  There is no option to load the route without recalculation and that is an issue.  Using your example above it does work the way you describe but I do not like that!  Lets just assume that B and C  are also shaping points.  Then If I am between B and 2 there is no way to call up and continue to use my route from basecamp (that may be 5,000 miles long).  The workaround I proposed (and the point of all this) is to not code them "Do not Alert".  That way they all show up on the next destination so you do not lose the planned route since you just select the next shaping point as you have suggested.  I know this will not affect most folks but I am a "power user"  and it is very irritating that when they 'Downgraded" the software from the Nuvi this issue was created.  BTW thanks for sticking with this.  Are you with Garmin?