Move only one symbol

Answer:

This is caused by dependency mode.  Dependency mode is a global setting which controls whether or not dependent symbols will move when a parent symbol moves.

Dependency mode status can be seen in the Status Bar at the bottom of the schedule.  It will show as either Dep. Mode: ON  or  Dep. Mode: OFF

To move symbols without other symbols moving, turn dependency mode off.

Turn Dependency Mode OFF:

On the Dates tab, Dependency Mode.