Working with 3D topology can be cumbersome at times, especially when you need to place points using precision. Altering the MicroStation Preferences settings can help when you need to snap points to existing polygons.
The Locate Interiors preference controls how closed shapes are found when issuing data or snap points in the element interior rather than at the edge.
The default value is Rendered or Filled which allows you to select a filled shape by its interior. Likewise, snapping to its interior will go to the center when the default snap is set to Keypoint.
To overcome selecting or snapping to closed shapes by their interiors, consider setting this option to Never. Doing so will force your snap point to use the active snap point on the element edge. .