problematic sketch on non-timestamp spline

I try to build a sketch on a non-timestamp spline. But many odd things happen.

 

Hope to have your suggestions. Thanks!

 

Fig.1 A non-timestamp spline built on YZ plane


Fig.2 A sketch is built on the spline plane


Fig.3 Sketch is handled in Sketch Task Environment.

                                           

Fig.4 "Save" is ENABLED in current Sketch Task Environment! Very odd. Generally "Save" is disabled in Sketch (not Direct Sketch!).


Fig.5 Upon exitting Sketch Task Environment, something is wrong with the result sketch.

 

If I create a datum plane on the spline first and then build the sketch on it, the resulting sketch would be ok. But "Save" is still enbled in the Sketch Task Environment.