Can you share your Sandcastle example with the “Share” button? See: How to share custom Sandcastle examples. Or using code-blocks. It’s hard to copy-paste this into Sandcastle without manually fixing characters like the quotes.
I think I can guess what the issue is though - if there are no samples for the VelocityOrientationProperty to sample, it’ll snap to a default. I posted a link here that explains this issue and has some discussion about how this may be fixed: Orientation problem at the end path VelocityOrientationProperty.