Client is creating an intersection point working in the assembly and selecting component objects. After selecting a face, the component the face belongs to is made the work part.
Solution
Added in NX1847 and later releases is the option:
File -> Utilities -> Customer Defaults -> Modeling -> General (tab) -> Allow Automatic Work Part Change
Change the default setting by unchecking it to work like NX12 and earlier releases of NX.
It is located at the bottom of the dialog.
Notes and References
Hardware/Software Configuration
Platform: INTL64
OS: window
OS Version: 1064
Product: NX
Application: SYSENG
Version: V1872
Function: SELECTION
Ref: 001-9559419