It's "farmland," not "uncultivated." And I don't have the link. It seems to me that roads created with the "isolated" tag have the same problem. And the road expressed as a dot is exported.
There is no such problem in general. I mean, if a road is not exported then it's something more specific, than just the "isolated" tag which I tested many times before (especially since it's a default tag now). Here is a very similar village:
https://watabou.github.io/village-generator/?seed=1026162478&tags=isolated,palis...
And that's how its exported version looks:
As you can see, both the regular (solid) part of the road and the trail part (dotted) are present. Anyway, if you will be able to reproduce the bug, please send me the link so can examine the case more closely.