ucs moves when drawing line in 3d

[jdfnnl]

I working to understand why AutoCAD sometimes shifts the ucs to the origin of a line I am drawing and other times does not. Here is a screenshot of an instance when the UCS appears where I am drawing. This is associated with also being able to see the line as it is being drawn:

other times the ucs does not shift over and I am unable to see the line following the cursor to the next point:

 

Ultimately I am trying to understand why I am often unable to snap to an intersecting line on the same plane when drawing in 3d. Does the UCS need to be configured on the same plane as the object of intersection. The green shape is an extruded polyline representing the exterior walls of a building. AutoCAD 2015.

 

[Michiel.Valcke]

You have asked a similar question in another post. Do you still have that behaviour when you turn 'dynamic UCS' off ? (use the F6 key)

https://forums.autodesk.com/t5/autocad-forum/circle-plane-different-from-ucs/td-p/12168323