Straight lines

[routeconverter]

Is there any way to avoid this?

yes

• pay Google
  
• use a free of charge Online-RoutingService
  
• use the Offline Edition
  

So if a route has already been calculated, don't query again when e.g. just zooming to a different level.

That is already happening.

One thing though, would I be correct in thinking that it does not affect what is saved in the file?

That is correct. It's just a display issue.

That is just a list of waypoints and no routing information, so whether Google has allowed the full route to be calculated or not, the file contents would be the same either way?

yes