@jfheath - For me, the greatest problem of recalculation now is the fact, that in connection with the traffic announcements from Garmin Drive there is some automatic recalculation of the route, which cannot be interrupted, no matter what are your settings on the Zumo XT!
If Garmin Drive sends a traffic announcement to the Zumo XT, that a road on your pre-planned route has a full closure, the Zumo XT will do a recalculation - this recalculation is only(!) announced with a voice message ('Road closure ahead, will use alternative route') and with no visual notice, just like a suggested re-routing because of a traffic jam or a building site, where you can choose to take it or not!
Recalculation Off, or Recalculation after Asking and also the setting in 'Traffic/Optimize Route' doesn't have any impact on the automatic recalculation of the route - you can't abort it!
This is a real bad thing - at all if the traffic announcement is completely false and this happened two times to me!
In June 2020 we were for ten days in southern tyrol, just one day after the border from Austria to Italy has been opened again after the first COVID-19 lockdown. After ten days in southern tyrol on the way back to Austria the Zumo XT suddenly showed 850km(!!!) instead of the planned 350km to the arrival of our overnight stop in Kärnten (Austria). This was about 250km from the Austrian border.
Not aware of this bug/feature(?), i stopped and tried to restart the pre-planned route - this worked for a minute or so and than it does the same recalculation again without any visual notice. I zoomed out the route (sadly not wide enough) to look for a possibly closed mountain street, but can't see anything!? A quick view on the newly calculated route shows me the problem - the Zumo tried to route me from Italy through Slovenia to Hungary, from there to Austria and in Austria back to Kärnten! As i have known the planned route a little, we continue to drive until we came near to the Austrian border.
There i could see the problem - i really don't know why, but there was a traffic announcement, that the border between Italy and Austria was closed (it was already open since twelve days!) and also the border from Slovenia to Austria also!
Last year in june the second time - after a heavy rain a street was partially closed (this was 30km from our hotel and there was a local detour) - Traffic system sends again a 'full road closure' to the Zumo XT and again a automatic, non interruptible recalculation of the route, which would take me for a 120km ride to our hotel!
This time it was easy - stopped the routing, turned off the using of traffic announces on the Zumo, restarted the Zumo and started the pre-planned route again!
I told Garmin every year of this problem and at first, the guy at the support confirmed me, that this shouldn't be so (the automatic, non interruptible recalculation) but nothing happens since the last two years - this bug/feature is already there!
This year i contacted the support again and they told me, that this is passed to the engineers, but they couldn't tell, when or if this will be corrected, because it is hard to understand this problem!?
It's quite easy - look at a local traffic announcement system for a fully(!) closed road, check if this road is also marked as fully closed in the traffic announcements of Garmin Drive and than plan a route in Basecamp, which uses the road. Put the route on the Zumo XT and let it drive a simulation - voila! No chance to stop a recalculation, if the road is marked as 'fully closed'! You don't have to be a software engineer to check this...
For me, it's a absolute no-go to have a non-interruptible recalculation of a pre-planned route, there is always the opportunity, that the traffic message is outdated, not right or completely false - also a closure for a car must not be a closure for all other vehicles, especially for motorbikes! The user MUST HAVE the last word, if he would like a recalculation or not!