Inaccuracy in Rhino/ Grasshopper- why and how to gets around it?

Some error that seems to be caused by a internal process when trimming and extracting a portion of the curve.

Case 1

I trimmed a vertical surface and the trimmed surface would not no longer vertical in rhino.

Case 2

I shatter a portion of a curve and the protion of the curve have a slight different from the original curve.

Case 3

I took three points from a circle and form a arc, and the arc with the same center have slight different from the circle.

The error is about 0.01 meter and it could be spotted when you zoom near.