There's nothing technically wrong with the style but the corner issue is being caused by a limitation with using the Z Offset in adaptive mode. It can be fixed by adding a larger corner segment and adjusting the increasing Corner Bevel value but because it offsets on the X axis perpendicular to the spline it won't necessarily give you the path that you need for a handrail.
In light of this I think the easiest and most flexible way to get a handrail that follows the correct path is to clone the base spline and move it up the required distance on the Z axis. You can change the spline material ID to 2 and then Limit the handrail spline so that it uses only this spline. In this way you can complete control over the path of the handrail and the corner problems are eliminated.
Please take a look at the attached file for an example.
I hope that helps, please let me know if you have further questions.