NX G1/G2/G3 pop-up appears once but disappears instantly.

While creating a studio spline, If you select one point from the candidates in quick pick menu list, G1/G2/G3 menu pops up and appears once but disappears instantly.
Therefore, it is not possible to create the spline while adding G1/G2/G3 constraints.

Step to reproduce: 
1.Open a part and create one or two splines by Studio Spline
2.Again, go to Studio Spline and Hold on your mouse near an end of the spline created with step1 until you see the candidates for the quick pick list > MB1

There are 2 splines like below. Waiting for appearing a sign for multiple candidates.

Moving your cursor and choose one point from the list.

** G1/G2/G3 pop-up appears once but disappears instantly.

Solution

The behavior is as designed.

Tips for/Workarounds: one of following
1. Do not move your mouse cursor and do not go to the quick pick list by moving your mouse. Keep staying at the point where you pressed MB1 and choose a expected point from the quick pick menu list by just turning the mouse wheel button.
2. Before choosing your expected point from the quick pick list, moving the menu for the quick pick list to near the selected start point for creating the spline.

Notes and References

Prior to NX1899 Series, the quick pick list was displayed near the geometries and often making the screen hard to see. Therefore, it's because the display location for the quick pick list has been fixed and improved since NX1926 Series so that it's displayed far from the selected point.

Hardware/Software Configuration

Platform: INTL64
OS: windows
OS Version: 1064
Product: NX
Application: DESIGN
Version: V1899
Function: CURVE

Ref: 002-8527183