I can also reproduce the exact opposite, routes that work perfectly well, so it can hardly be down to a bug in BaseCamp or I'd see it. What I can't replicate is your system, or the maps and workflow you use.
I can also produce routes that work well. Nobody said it happens all the time or under all circumstances. What do you think, that people wasting their time making something like this up for the benefit of...erm...nothing?
Attach such a route here then, and confirm which map it is, and I'll have a look if I can … I have various OSM maps and CN EU and CN NA.