Base Camp Route Shapng Points Vs Waypoints

You don't say which device you have, modern Garmin auto devices don't expect you to pause and wait at a waypoint. As to which you use, the advantage of shaping points is that you can skip them or miss them slightly without issue. If you don't want that flexibility set them as waypoints.

Note on many devices you may get a recalculation depending on the options set within BC compared to those set on your device.

Sorry - I have a nuvi 2597
I know I went past the waypoint, it's a narrow 1 way street, but after I had gone away, the device wanted me to go back. I did so to check it out, I got to the waypoint again, stopped and I noticed the device seemed to acknowledge my position and setup the next leg of the route. But the next leg was to shaping point (won't alert) point, but it recalculated without me asking and directed me to the next waypoint. It didn't take me past the shaping point.
I do want shaping points in many cases, I was assuming they would help maintain the route (i.e. cause any re-calc to again include them).
I can't see any options of the nuvi where it says "no re-calc" is there?
In Basecamp I am always wary of a recalc doing my routes in especially when I change the maps but I'd like also to lock the route. Is this possible? If so - how?
Alan

There is no way to lock the route. If for any reason your nuvi has to recalculate it will do so based on the settings set on the device.

The device only has options for Calculation Mode [Faster Time, Off Road, Shorter Distance, Less Fuel]. These can be set individually per route. And a route has Optimise Order which warns of the intention to strip Shaping Points.
So if the Shaping Points are not stripped, a recalculation should continue to include them.
I'm at a loss as to how the route changed during use and omitted the shaping point.

Device behaviour varies as Garmin updates its algorithms ... If a recalculation occurs then shaping points from the next waypoint will be included but may be skipped between where you are and the next waypoint.

Note this will include any avoidances set.

This sounds odd. It certainly fits with my observation today but I am still unclear as to what prompts a re-calc. I certainly didn't select to optimize.
also...

....but may be skipped between where you are and the next waypoint.

what would be the logic behind this arbitrary modification?

Your device will recalculate if for example you go off route. You say you missed a waypoint and turned around, that may have caused it.

If you really want to hit a shaping point and a recalc happens then you'll need to convert that point to a waypoint, then select the route again and select that point.

OK - that makes sense, if I miss a waypoint I will pay attention to the route. Perhaps I would need to stop and restart the route at that point. When you start a route it gives you the option of selecting a start point. I notice you cannot start at a shaping point. So I'd need to start at the current location (waypoint) in this example.
At least I am becoming aware of the nuance of the device. I can't stand unreliability and this is just knowing how to predict the behaviour.

You can though do what I suggested. Convert the shaping point to a waypoint and then restart the route and select that point.

OK - I just checked the track logs and I can see that the waypoint I installed was actually about 10-15m away from the closest I could get to it.
So I need to know what technique or action I need to take to ensure that I hit waypoints and thus avoid a re-calc or indeed a case where the device keeps calling me back to the waypoint. I don't need that either.
Seems a bit onerous to have to stop exactly on a waypoint to have it cancel. That's probably why it cancelled when I returned and stopped for a minute. Even though I was not closer than 20m it finally acknowledged.
Any suggestions?