You can see in the Plan View of the Roadway Designer that the end condition is a blue line where it is tying into the terrain. In the areas where the end condition does not solve, it appears that the solution would be outside the extent of the existing surface (white lines). The blue lines are tracking and appear to intercept and would 'cross' outside the boundary of the existing. So in these areas it cannot find the target and thus will not solve.
You probably need a solution/end condition which is a steeper slope so it can intercept with the existing surface. You can do this with an additional end condition in the template at a lower priority or you can create end condition exception to override the template EC over this particular range.
