I use the "Elevate Lines" command quite a bit when elevating my curb returns. One thing I have noticed is that if the offset line tolerance is not zero, there will be nodes created beyond the horizontal geometry when elevating arcs when the offset tolerance is set to anything greater than 0.0000.
The values that are created are small and probably dismiss-able but it is interesting that these vertical nodes are created beyond the horizontal geometry. Based on the help guide, the offset tolerance should be the perpendicular distance to the intersection and there is in fact a vertical node being created at the intersection. In the case of the curb returns I am working with, this would be the end of the arc.
The work around is set the offset tolerance to 0.0000. I am curious if this is intentional or potentially a bug. I cannot think of a case where I would want a vertical node to be created beyond the horizontal geometry of a linestring automatically.