Good luck finding the cause Guys, I admire your commitment!!
Some comments that may help your fault finding:-
Regarding my original post, when we go on tours I always create the routes in basecamp in the evening. I then connect everyone's satnav to my computer at breakfast and download the day's routes via Basecamp (or Mapsourse in the dark ages).
I've done this for years using a combination of Mapsource and Basecamp on a MAC and a PC, to Garmin Zumo 550, Zumo 660, Zumo 595, Nav 4, Nav 5, Nav 6 and most of the time all is OK but sooner or later someone's satnav will show the problem the OP sees.
Re-calculating the route using a different profile always fixes it.
For the rest of the trip the devices that showed the problem continue to do so every morning which tells me that the problem is with the device, not Basecamp / Mapsource preferences.
One of our group had the problem on a tour. After he got home he reset his satnav to factory settings and reloaded his maps. Next time I uploaded the route it was fine.
Interestingly I also publish routes for our groups regular Sunday Rides as GBD and GPX files on my website, no one has reported the spiky problem when using those routes.
I've wasted a few hours trying to find the root cause, but once I found the easy fix I lost the will to dig any deeper. I guess its a lazy 'treat the symptoms not the cause' solution but I decided my time was better spent riding the routes I created
Some comments that may help your fault finding:-
Regarding my original post, when we go on tours I always create the routes in basecamp in the evening. I then connect everyone's satnav to my computer at breakfast and download the day's routes via Basecamp (or Mapsourse in the dark ages).
I've done this for years using a combination of Mapsource and Basecamp on a MAC and a PC, to Garmin Zumo 550, Zumo 660, Zumo 595, Nav 4, Nav 5, Nav 6 and most of the time all is OK but sooner or later someone's satnav will show the problem the OP sees.
Re-calculating the route using a different profile always fixes it.
For the rest of the trip the devices that showed the problem continue to do so every morning which tells me that the problem is with the device, not Basecamp / Mapsource preferences.
One of our group had the problem on a tour. After he got home he reset his satnav to factory settings and reloaded his maps. Next time I uploaded the route it was fine.
Interestingly I also publish routes for our groups regular Sunday Rides as GBD and GPX files on my website, no one has reported the spiky problem when using those routes.
I've wasted a few hours trying to find the root cause, but once I found the easy fix I lost the will to dig any deeper. I guess its a lazy 'treat the symptoms not the cause' solution but I decided my time was better spent riding the routes I created