Sometimes it may occur that adjustable parts or assemblies are moving
unexpectedly while dragging or setting relationships.
Solution
Please check if the part/assembly is placed by a "ground" relationship.
"Ground" relationships will become "flexible" if a part/assembly is defined
as adjustable. This is "works as designed", and is necessary for
calculating different shapes/positions of adjustable parts (and assemblies).
So to resolve just change the "Ground" relationship e.g. by using 3
relations to reference planes.
Notes and References
Hardware/Software Configuration
Platform: INTEL
OS: window
OS Version: 864
Product: SOLID_EDGE
Application: ASSEMBLY
Function: SIMPLYMOTION
Ref: 002-7008832